Project Latte - 996 Coolant Intermix Resurrection

Introducing my 996 project, which I am calling Project Latte for reasons that will become very apparent later in this thread...... To start with, some facts. It is a 1999 C2 Manual in Ocean Blue with Savannah Beige interior. It has a sunroof, sports seats, extended leather, Litronic pack, and the optional LSD. The previous owner advertised it for sale due to it showing all the symptoms of a cracked cylinder head. I had been looking for a 996 for a month or so, and although I didn't necessarily want a project as big as this, the price it was advertised for meant that, assuming I did the work myself, I could spend what I was prepared to spend on a good 996, but end up with a nearly completely sorted car. I saw the advert on a Wednesday, messaged and spoke to the owner the day after, then spent the next few days doing as much research into parts prices as I could to make sure that my plan was feasible. I then viewed the car on the Saturday and agreed to buy it. The car had a thick folder of service history, but unfortunately appeared to have fallen victim to a failed waterpump and the resulting cylinder head crack. At the time of viewing the car, this was not confirmed. The previous owner had issus with the car overheating, and had taken the car to his trusted garage, who did all the tests they could to find other, easier to fix causes for the overheating, but they determined that it was very likely a cylinder head crack. I agreed to buy the car knowing this, and arranged to have the car transported back to my unit.

The car then sat for about a month while I sorted out some other life things and made some arrangements. In this time I fitted a new battery as the old battery was completely dead which was very annoying when I needed to move it out of the way of other cars. Oddly enough, for the severity of the coolant intermix, the car started and ran very well, and never showed any sign of smoke or steam from the exhaust. Still, the evidence of milkshake on the dipstick and in the coolant reservoir told me that the engine most definitely needed to come out. So I made some arrangements to borrow a lift for the weekend and got to work. Things didn't look too bad underneath, but I was in for a bit of a surprise when I drained the oil...... I hadn't expected it to look particularly healthy, but this was on a different level of bad. And here we see why this project has received its name. With this discovery, I was feeling especially justified in going ahead with the engine removal. The rest of the engine removal went pretty smoothly, and after about 10 hours work, and only a small piece of my thumb missing, we had the engine out, gearbox off, and everything loaded into the back of my dad's Transit.

Looking forward to reading this story......subscribed.

It makes for interesting reading…….looking forward to seeing your updates

Great project ! and a great way to end up with a well sorted 996 at the end of it.

Following a bit of a struggle to get the engine out of the van, and onto the engine stand in my garage, we got to work stripping the engine down. This again was pretty straightforward, although the slip-and-slide created by the infinite supply of oil-based latte dripping out of the engine made things a bit interesting at times. It took us about 14 hours over 2 days in a very warm garage, but we had the engine pretty much completely disassembled. Unfortunately, 8 of the 12 exhaust manifold bolts lost the fight with my breaker bar in the process, but that is an issue I will deal with later.

I'm pretty sure this car was mentioned on here in one of the threads as being a good car to buy and repair. The bores look lovely whats the mileage?

So those posts brings me up to date with where I have got to so far. This evening, I finally had time to go back out to my garage to get started on finding the crack that was supposedly in one of my cylinder heads. In preparation, I had purchased a welding crack detection kit, which I had intended to use to find the crack as I couldn't see anything on either cylinder head when we intially took the engine apart. However, upon giving the 1-3 head a quick wipe with brake cleaner, the crack was immediately obvious. It was quite odd seeing the crack, relieving in a way as it meant that all the work so far wasn't for nothing, but also slightly concerning as I now have a clear problem that I need to find a solution for. From all my research so far, this crack seems to be one of the most common places for a crack to develop, and especially since it is on the 1-3 cylinder head. This does bring me some comfort though, as my hope was to get the crack repaired rather than to find a new head, and I believe that a crack in this location is relatively easy to fix. I would certainly appreciate any comments or feedback on this, as I am currently just basing these assumptions off research I have done with others who have had this issue. Currently, my plan is to contact NWS Motorcast in Shropshire as I have seen their name mentioned before in other threads about this issue. As well as this, in the interest of doing things properly as I would like to keep this car for a long while, I'm intending to drop the case halves off at Hartech to have their Nikasil liners fitted. I am slightly conflicted about this, as there isn't actually anything wrong with my cylinders, but I feel that it will be worth it for futureproofing and my own peace of mind.

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I have been looking but I don't remember seeing it mentioned on any threads recently? It's on 134000 miles, and yes I do agree that the bores look good, although I noticed a fingernail-catching groove in one of the bores when I was in my garage this evening. As I mentioned in the last post, I'm intending to get the Hartech Nikasil liners fitted, which does seem a shame given how nice most of the bores are, but I just don't think I'd ever get the thoughts out of my head if I just rebuilt it without getting the Hartect treatment done.

yep i agree ,getting the hartech treatment is the best option as you're doing the work yourself and just getting them to do the machining it's well worth it.

Seeing as you've saved yourself a bucket load by doing the DIY, are you going to 3.7 if you get Hartech doing the work? Least then you have a cherry on top when you get the car back up and running. Also worth asking them about the cracked head and broken manifold studs. They get the studs out in no time and may also have a solution for the cracked head. There's also a guy in Italy who repairs the heads and claims he's never had one fail yet (he's in Hartech's Porsche engine Guru's page on FB).

I would love to go to 3.7, but I'm already going to be reaching the limits of my budget as it is, so that won't be happening unfortunately. Also, as far as I know, they only do the 3.7 conversion if you drop the whole car off with them. I've borrowed a Stomski jig to deal with the manifold bolts, but good point about the cylinder head, I'm going to email Hartech today with my questions.

Great work and write up. Following with interest.

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Get a price off them for the increase if they'll do it. I know they've done it for other members just dropping the cases off. You just won't get a warranty with it. I think you'll be surprised at the cost difference. I can get you the details of the guy in Italy who repairs them if you get desperate.

Been in contact with Hartech this morning. Cost for keeping original capacity with new liners is £5040, upgrading to 3.7 would be £7500. So very much out of my budget. I've also been in contact with the company I was hoping to send my cylinder head to, but they're told me they're closed for the time being. Any recommendations would be helpful.

I understand if you don't have the extra dosh, but that increase will add more than £2.5k to the value of the car once done compared with a standard rebuild in my opinion.

Following with interest, Thanks for posting, wow look at that oil !!

Great project!! Keep it up! In terms of the head, there was a guy in the US, he documented it all on rennlist I think, he had the same exact issue, same spot. He got it welded, when I came across it, he already had something like 20k miles of happiness and was still going strong. Regarding the bores, I would either leave it as it is or get Westwood liners for peace of mind. Just my thoughts.

Yes I think I've seen those posts, they're the main reason I think that mine could be repaired. However, finding someone who can do it is proving difficult, everyone I contacted yesterday either told me that they don't do this kind of work at all, or wouldn't be able to tell me if they could do it until they did a test run on it. I also didn't get any idea of the cost of repairing it from anyone, so while I'm still looking for someone who could do it, I'm also looking at replacement as well. If anyone has had their cylinder head repaired before or knows someone who has, I would really appreciate any information on who they got to do it.

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Makes sense, you are doing it the right way. Keep us updated

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i was thinking the exact same thing - worth putting it on a credit card while its being done - its got to be worth the extra all day long from a resale point

Some interesting and helpful info in this thread: A Thread '3.4 cylinder head crack' 14 Aug 2019 Hi all I've not posted for a while, as per title I've had some issues to attend to with oil in my coolant. Combined with having a baby 6 months ago I've only just gotten around to taking the engine out of my 3.4 for the 2nd time in 12 months. Initial diagnosis is a crack in the cylinder head on bank 4-5-6. This appears to be between one of the core plugs and and the oil gallery underneath the cam follower housing. Obviously a new head is out of the question due to cost. A 2nd hand head could be an option but I'm worried about having a similar issue so keen to know more about a welded... Armagreggon85 Replies: 28 Forum: Porsche 911 996 (1997-2005)

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........and the fun factor and saving on fuel (as it'll be more economical).

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I think I've read that thread before as well. Unfortunately, the company mentioned (that Hartech also said they approved of) is one of the companies I contacted yesterday, but they told me that they are currently closed. Interesting what they say about modifying a 3.2 head in that post, I might contact Hartech to see if they could do that work too.

years ago you could get this type of work done in a shed in coventry by a guy with a roll up in his mouth - knocking out head welding for pennies...............the skills shortage is terrible now...............

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Oi I resemble that!!

I know.......................where's your roll up!!!!

I only smoke spliffs and thought I'd get in bother posting one of them up.

Following along keen to see how it pans out. Is it not easier to buy a second hand head without a crack?

Potentially easier yes, but I would imagine it will be more expensive. I'm looking at both options currently but it will come down to whichever option is cheaper. Currently the cheapest cylinder head I can find online is around £1500 and it's in Latvia so I'd have to pay extra on top of that.

**EDIT: Apologies, got part number wrong. 605 euros delivered: Cylinder Head 996104201 6R, M9670 for PORSCHE www.athousakis.gr £1236 brand new: Dedicated to your Porsche needs Design 911 supply car parts, spares and accessories, to both retail and to the trade. Our car product and accessory range includes brakes, exhausts, tyres, wheels and panels and interiors. #Porsche #ServiceCentre #Essex www.design911.com

Also, give 9-apart a call. They sell 2nd hand heads and may have one in. Had one up for £875 a while ago: Pardon our interruption...

Plenty of 3.2 Boxster heads available , they're the same as the 3.4 only you'd have to drill and tap the M8 threads for the exhaust hanger in the 2 posts, easy job. https://www.ebay.co.uk/itm/267630250222?mkcid=1&mkrid=710-53481-19255-0&siteid=0&campid=&customid=&toolid=10001&mkevt=1

I've been researching the 3.2 heads today, it seems like there's also a slight difference in shape inside around the valves. I'm going to call into a local machine shop tomorrow and show them my current heads to see what they think about machining the 3.2 heads to match.

Skipping ahead somewhat, I've been reading through the workshop manuals to get a better idea of what I'm in for when I get to putting my engine back together, and I saw that in the steps for refitting the heads and chains and setting up the timing, Porsche recommends using a special tool to put the correct tension on the chains while the timing is being set. They refer to it as auxiliary chain tensioner special tool 9599, and the manual calls for 3 of them to be used in place of the actual hydraulic tensioners during the engine build. I assume this is because the hydraulic tensioners won't be putting the correct tension on the chains when there is no oil pressure, but given that these tools are about £70 each and I'd need 3, what have those of you who have done DIY engine rebuilds done about this? Is there a DIY tool that can be made, do you not bother, could I borrow them from someone?

The previous owner of my car had the heads repaired, I’ve got a very basic invoice from NWS Services. £1300 Quick search it looks like this may be the company who did the work ? https://nwsmotorservices.com/reconditioning-and-remanufacturing/ Do Hartech not do it? That’s a real surprise if they don’t ? I’ve also seen stanwood engineering mentioned Stanwood Engineering - Home

NWS is one of the places I've been in contact with already, but they told me that their machine shop is currently closed. Hartech have told me that they only replace cracked heads, never repair them.

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Not needed, just use the tensioners I have replaced the timing chains on mine amongst other things and not had any problems. You would only need 2 anyway if you were to buy them as the engine is timed one bank at a time.

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Complete 3.2 on eBay https://ebay.io/m/ACvdkD

You also have to drill/tap the top mount posts as well , they're all blank on the 3.2. I'm not sure I'd want it repaired , unless it was Xray'd so you know how deep the crack went. It's always niggle me having a weak spot.

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Thank you. I did see someone mention just manually pumping the original tensioners with oil, so that's probably what I'll do. Yes the more I look into this problem the more inclined I am to replace rather than repair. I don't suppose anyone would know what sort of price a machine shop would charge to machine away the extra material around the valves on a 3.2 head?

I expect the differences in the combustion chamber are to do with compression ratio. I would get a piece of perspex to cover the chamber, drill a hole in it, stick down with some grease and measure the CC with fluid / syringe. Idea is to match the CC of the chamber by machining the 3.2 head. I would look for a head porting company - this type of work should be basic stuff for them.

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the difference is 3 ccs it's hardly noticeable, i'd just use a dremel and do a bit of DIY porting

I'm confused ..again Both have same crank 3.4 = 11.3:1 cr 3.2 = 11:1 So removing material from the 3.2 will lower the compression ratio even more won't it?

That has certainly occured to me. I haven't got a Dremel but I've got a die grinder. I suppose it would be quite easy to make a template of my original head which I could use as a guide. My only concern would be the surface finish I'd end up with, do you reckon that would cause any issues?

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I'm also mildly confused but I think the point is that if you machined off part of a 3.2 head when it's still on a 3.2 block then yes you'd end up with a lower compression ratio than 11:1, but when you put it on a 3.4 this makes it higher than 11.3:1, machining the head brings it back down to 11.3:1? Either way, the heads are identical apart from some additional material around the valves so if I remove that material I'll essentially have a 3.4 head which is what I want.

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i think it'll be fine, you can get fine grit sand paper drill bits to smooth it out to the desired finish.

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it's down to the bore size i reckon,

Some interesting threads in the past about it (see below). I've also asked Mistercorn just now if he can help as I think he's fit a 3.2 head on a 3.4 in the past. A Thread '3.4 cylinder head crack' 14 Aug 2019 Hi all I've not posted for a while, as per title I've had some issues to attend to with oil in my coolant. Combined with having a baby 6 months ago I've only just gotten around to taking the engine out of my 3.4 for the 2nd time in 12 months. Initial diagnosis is a crack in the cylinder head on bank 4-5-6. This appears to be between one of the core plugs and and the oil gallery underneath the cam follower housing. Obviously a new head is out of the question due to cost. A 2nd hand head could be an option but I'm worried about having a similar issue so keen to know more about a welded... Armagreggon85 Replies: 28 Forum: Porsche 911 996 (1997-2005) M Thread 'Project = Boxster engine into a 996' 8 May 2019 This thread has been split out from my 2001 project car thread, as although it is all part of the same grand plan in terms of engine development, it isn't really anything to do with that particular project. This part of the project involves buying in a full Boxster 3.2l engine, seeing which ancillaries are the same as the 3.4l M96.01 engine so that I can use those for checking clearances, and then have the rest of the engine rebuilt as a 3.7l engine for my C2. The thinking behind this is as follows: 1/ The overall project aim is to develop 3 sets of camshafts for different engine... MisterCorn Replies: 52 Forum: Porsche 911 996 (1997-2005)

Guys, this thread is turning into such an impressive school!!!

CR also dependant on piston crown design

Mistercorn says you just need to do the tapped holes for the hangers.

Some more progress today. Took my case halves and heads down to the local jet wash to get them nice and clean before machining work and reassembly. Got a few odd looks and some very wet feet but they came up pretty decent after they dried in the sun.

Then got to work on stripping down the crank ladder and IMS assembly. Everything looks pretty good, especially the crank. The bearings show some wear in places but the crank itself looks nearly brand new. The IMS chain guides looked pretty bad though so glad I'll be replacing them. My engine has already had an upgraded IMS fitted by one of the previous owners but I'm debating what to do about it in the rebuild. I need to take a close look at it but I'm inclined to replace it with an original double row bearing as they don't seem to go wrong.

Yep i replaced mine with a standard new double row and i have some stronger machined centre pins to fit without the groove in them if you're interested .

That sounds like something I'd be interested in. Where did you get the new bearing from?

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Would they not fit in the dishwasher?

Reading the thread above that Baz from Hartech is in , I'd say a straight swap without any machine work would be fine but is an option but as mentioned you have to get the head and cam cover together as a pair with matching numbers. CR is increased slightly then! I'd be happy with that. If you're intending on keeping your 3.4 for many more years as I am , I'd say it wouldn't be too silly to get a pair of heads from a 3.2 if they ever come up at a good price and store them away just in case.

Also, would it make sense to swap both heads as the CR on one side would be different to the other or would it not matter?

I reckon Baz would've suggested that if it was necessary , I can't see there being a noticeable difference. At least the 3.2 head offers another option when this happens.

Well funny you say that, because this is the email I received from Hartech when I asked if they had any 3.4 heads in stock that I could buy: "We're also currently looking for a 3.4 head for another customer and, so far, we've had no luck. We've found a few for sale, but they're priced higher than we're prepared to pay. It is possible to machine a 3.2 head to suit, but it's not something we've done before. Because of that, it's not a job we'd be comfortable taking on, as if any issues arose, we'd be responsible for the outcome. The last time we encountered a similar situation, we replaced both heads with 3.2 heads instead. This does lower the engine's compression ratio slightly, probably not by a significant amount, but it's still something worth considering. I'd recommend doing a bit of research into the implications before deciding." So if I didn't want to do any machining work, the best option would be to fit two 3.2 heads. But I think I can probably DIY the machining work needed so I'm happy enough to just replace one head with a 3.2 head.

£190 shipped: https://www.ebay.co.uk/itm/256810140166?mkcid=1&mkrid=710-53481-19255-0&siteid=0&campid=&customid=&toolid=10001&mkevt=1

I asked about that one yesterday to use as my exhaust bracket mod jig but I need 4 of them (L&R for 3.4 and 3.6) so it's too expensive even at that. Core plugs had been tapped out for motorsport so it's had a hard life.

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You never know, someone on here might be able to sell you a cracked one for peanuts.

I'd certainly be willing to part with my cracked head once I've got my engine sorted

What were you hanger lower fixings like? https://911uk.com/attachments/1772485790038-jpeg.142842/ Thread '996 Rusty Exhaust Hangers' 2 Mar 2026 I thought I’d do a wee write up on what I did to recycle my rusty hangers. The hangers on 996s and 997s often corrode really badly in the lower section that bolts to the head near the manifolds. The hangers are made of Stainless 15mm tube but with mild steel ends and also the central webbing section is mild steel. This is what the lower laminated section often looks like This is usually the only part of the hanger that is beyond help , the central webbing and the top section don’t get as bad due to their location Top section with very light surface rust ... Uncle Monty Replies: 22 Forum: Porsche 911 996 (1997-2005)

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this looks like a .2 three chain head unfortunately . won't fit.

@Uncle Monty As bad or slightly worse than yours. I'm planning to just cut through the thin section between the rods and treat the rest with rust converter. @Hooner where did you source a new double row IMS bearing from? Looking online there seems to be a number of different places but not sure where to trust.

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direct message me if you want.

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Rust converter won't last 1 week Send me the head and your hanger and I'll weld a new stainless end on it for you. https://911uk.com/attachments/1772486688758-jpeg.142848/

Had a look at my IMS bearing this afternoon, it appears to be an LN bearing, but I can't really work out much else about it. All I know is that it was fitted in 2015, and the car has done about 25000 miles since then. It seems silly not to replace it since I'm doing all this other work, but I'm a bit stuck with what option to go for. I'd like to go back to an original spec dual row bearing and just take the seal off, but as @Hooner has pointed out, I'll need a new centre bolt and flange cover as the LN one won't fit an original bearing. But then I can't make use of the upgraded LN bolt and cover because it doesn't seem like you can just buy the bearing that they use in their kits.

I did my Boxster roughly then and I think it was called the IMS Solution , total waste of money as my dual row was tip top but the flange was leaking and I don't think you could get a seperate seal back then but I'm probably wrong.

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the LN bearing is a weird size held in by that circlip, the original double row is wider , Uncle monty may have an original flange cover and spring clip that fits around the bearing ? if you decided to refit an original.

If you’re getting liners with Hartech I’m sure they offer to machine the block and modify the IMS shaft to accept the later 997 bearing.

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@Uncle Monty are the rumours true? I've just bought a flange cover on eBay that seemed pretty cheap but I'll still need the spring clip. Can't find any information or part number for it anywhere.

They did that for Lee Sibley, For reference, this is what they supplied him & cost involved:

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I'll have a look.

So just doing some research on where to buy an original spec double row bearing from, I believe the part number for it is BD20-17 A DDUA17 NX01 NSK. What is confusing me is big difference in prices depending on where you buy from. https://www.123bearing.co.uk/bearing-housing/deep-groove-bearing/double-row/bd20-17-a-ddua17nx01-nsk - £102.94 https://www.sp-spareparts.co.uk/en/p/bd20-17-a-ddua17-nx01-nsk - £40.32 https://shop.rolling.hu/catalog/product/143308 - €33.47 https://www.2rs.eu/index.php?route=product/product&product_id=182991 - £41.64 https://www.cuscinetti.net/nsk/88222-bd-20-17-a-ddua17-nx01-nsk.html - €124.36 I'm tempted to go with SP-Spareparts but I'm suspicious of why some suppliers are half the price of others.

Hooner is the one to ask, he's the bearing guru. Curious why you don't just leave the LN one in?

That was my plan originally when I bought the car and saw that it had had an LN bearing fitted, but I did some investigating and found that apart from their 'IMS Eternal Fix', which replaces the IMS bearing with a plain bearing similar to the crank bearings, all their other options have at most a 6 year service interval, and since mine was fitted in 2015, it's well past that. I'm going to replace it with an original double row, remove the seals, and use Hooner's upgraded centre bolt.

Got a bit of tidying and cleaning done this afternoon, some of these bolts were absolutely caked so it was a surprise how well they cleaned up. I also started trying to tidy up my fuel rail, its not too bad but a bit crusty towards the back. Undecided what to do about it, but I'm thinking rust converter and then some high temp paint to hopefully stop them getting worse. While I was cleaning the rust off I did notice what I initially thought was a crack in the fuel rail, but looking closer it seems to be where two pieces join and the gap hasn't been fully welded. Has anyone else noticed this before? Should I be worried? As well as the fuel rail being a little crusty, two of my injectors are a little bit worse off than the rest. I think the other 4 will clean up ok, but the 2 on the left have swelled and deformed the plastic part. Would just replacing 2 and leaving the rest alone cause me any issues? Looking online I mostly see injectors with green / turquoise plastic rather than my dark blue ones, are there any differences? Last question, I promise. I was trying to clean out the oil/coolant mix from the oil cooler and I noticed that the hose attached to it is a bit of a funny shape just above the hose clamp. I can't tell if it has swelled / deformed, or is this just the shape it should be? Thanks to everyone who has answered my questions so far. There will be many more.

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Is the spring clip the one that goes around the bearing in the groove?

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yep thats the one

That pipe on the oil cooler looks swollen to me.

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I'll have a go at this.. Bolts have come up nice , the coating on these is called Zinc Flake or Geomet , yours have fared well , they're not cheap to buy. Fuel rails look normal for a UK car , they started life as a gold passivate , I submerged mine in white vinegar for a week (weak solution) which removed all the rust , etch primed them and then Gold Hammerite. https://911uk.com/attachments/1771431163753-jpeg.141643/ If you do this make very sure you clean the insides out really well so you don't block an injector with crap. Injectors look normal. If you can afford it I'd get a full new set and a new FPR, if you can't replace the 2 worse ones (Bosch only) and make sure you know where you put them, I did the same and put them on Cyl 1&2 for ease. You can get kits to recon the others but you can't do anything about the internals just the filters , nozzles and Orings. Also check the earth connection for the injectors , it's an m6 bolt on the end of the head with 3 brown wires going into it , they break easily. Worth doing a proper job on them. https://911uk.com/attachments/img_7478-jpeg.134381/ Oil cooler hose does look like it swollen , I'd replace it . If you read my thread from Page 6 it covers all this. https://911uk.com/porsche/1998-996-c2-manual-rolling-restoration.125999/post-2773819

Your FPR port on the fuel rail does look a bit crusty but it's probably alright , if in doubt you could have a look on ebay in the US from a dry state. something like this , also has clean looking injectors....in fact I might buy it. https://www.ebay.com/itm/226668852494?mkcid=1&mkrid=711-53200-19255-0&siteid=0&campid=&customid=&toolid=10001&mkevt=1 from California...what a difference

I've got a 3.2 head on my workbench at the moment and there are a couple of differences at least to my 3.4. The one mentioned is the drilling for the exhaust hangers, but there is another important change and that is the drilling for the inlet manifold which is different also due to the aluminium lower intake on the 3.4. Where are you based? Are you local to London at all? I'd be happy to have a meet up one evening and we could compare heads (not like that get your mind out of the gutter)

Thanks all for the help. Had a bit of an exciting day yesterday as I dropped off my case halves at Hartech to have new liners fitted. I was told it was a 3-5 week lead time at the moment so that gives me a few weeks to get everything else sorted so that I can get straight onto reassembly when I get the cases back. Thanks Monty for the advice, I'll do something similar to you with my fuel rails to help protect them for any more corrosion. I think I'm going to try and find 2 good used injectors and replace the O rings on all 6. My only question with the injectors is about whether or not the green/blue injectors are any different to the dark blue ones that I've currently got? And @Uncle Monty I presume when you say keep track of where you put them you mean so that if there's an issue on those cylinders I'll know why? And I assume cylinder 1 and 2 are the easiest to get to with the engine in? I've ordered a good used oil cooler hose, thanks for confirming my suspicions about it. And @Shalmaneser cheers for pointing that out, I've compared my current heads to the 3.2 head that I've bought, the holes for the intake manifold are definitely different but the bosses for the correct holes are still on the casting so I'll just have to add those to the list of new holes I'll need to drill and tap.

There are some copies of the Bosch ones that D911 sell as OE Match that are light blue but personally I wouldn't go near them , it's just not worth it , but I think Bosch also changed the colour so the one above might be Bosch , you'd have to ask the vendor. KSM are purple and copies with mixed reviews. I found 2 new ones for £60 on ebay so I put them in cyl 1&2 purely so I wouldn't forget , if I find some more new ones I'll carry on to 3,4,5 & 6. I'm fairly certain one of mine was dripping as my oil always smelled of petrol and now it doesn't. I rigged up a can of carb cleaner to test them and one dripped after i had turned it off. Spray pattern on all was good though. Hooner and I both fitted a new Bosch FPR that wasn't the one designated for the 996 but it's identical really and much cheaper. Good luck , it's a great thread with a great title and now it's getting really exciting. Mine's running like a sewing machine and such a laugh to drive.

I would definitely warn against non-original injectors, and don't mix n match!

Just doing a bit more investigation on the differences in the fuel injectors. Mine, the dark blue ones have a 0280150455 part number, whereas all of the light blue/green ones I find have a 0280150470 part number. Both, when they are original factory fitted parts, are Bosch, both show as fitting a 3.4 996, and apart from the colour they look identical. I did some Googling and came across this link: Club G40 - The Polo G40 Owners Club UK Which contains a table showing Bosch fuel injector part numbers, and their corresponding flow rates and resistance. Both the 455 and 470 injectors have identical flow rates, at 229cc/min, and resistances, at 12 Ohms. I also found this website, which confirms the same: WitchHunter Performance - Injector Cleaning & Flow Testing Services So that's good enough for me, I'll replace two of my rusty injectors with some tested used light green ones.

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I've bought this had it sent to my brother in Michigan

I'm not jealous at all..... Would have liked to buy it if I had the extra budget but for now some rust converter and Hammerite will have to do

@Uncle Monty can I ask how your camshaft position sensor is holding up? Reason I ask is I'm going to replace mine and was looking for what to buy one, and I found that GSF has them for what seems like an absolute bargain: https://www.gsfcarparts.com/products/camshaft-position-sensor-hel6pu009121-591 . £13.79!

Yeah all good. Not sure which I bought but yes that does seem a good price and it's Hella. I think they're Chinese but probably good quality. Just checked and yes I bought a Hella from ebay £47. Hella 6PU 009 121-591 same as yours..get it. I'd replace the crank sensor too...mine was properly stuck in there. I wired mine up wrong , got the plugs mixed up but luckily Hooner noticed and saved me a brain hemorrhage later for which I owe him a beer or two. Did you get the clip?

Perfect, sensor ordered. Already got a crank sensor on order too, mine got destroyed in the process of removing it. Not got the clip yet, should arrive tomorrow I imagine, thanks again.

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mine was £65 quid, i got a Bosch one though

So I've had a few exciting deliveries today. First, and most importantly for the original topic of this thread, a new 1-3 cylinder head has arrived. It is, as mentioned previously, a Boxster 3.2 head. I had a good look at it this evening and compared it to my original 3.4 head, and as expected, the differences are: 1. Slightly different shape around the valve openings in the combustion chamber 2. Different mounting holes for the intake manifold. 3. No holes on the exhaust and intake sides for the exhaust backbox hangers. However, the raised bosses for the correct holes for 2 and 3 are in both castings, so it should be pretty straighforward to install some tapped holes to convert the 3.2 head to use the fittings of the 3.4. The plan for the differences in the combustion chamber is to borrow a die grinder for the weekend, make some paper templates of the 3.4 head, and let it rip. I will of course also need to remove the exhaust manifold from the 3.2 head, but it can't go any worse than 6/6 snapped on my original head, and in any case I've got a Stomski jig to drill them out.

I also received a new (to me) rear anti roll bar to replace my old one, which snapped and fell off the car completely on its own while I was undoing the mounts on the opposite side. The new one isn't in amazing condition either, but it's definitely more solid than mine and should clean up nicely with some rust converter and paint. It's also a 19.8mm thick one from a C4 as opposed to my original 18.7mm bar, so I'm considering this an upgrade.

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that 3.2 head looks like it's come off an engine thats suffered some intermix, i hope it's ok

And last update for today. I mentioned that I was going to buy 2x 0280150470 injectors to replace my 0280150455 injectors as I believed they were identical. Well feel free to laugh. My original is on the right, covered in tape. While externally they are identical, and their electrical specs are identical, it seems the nozzles are different. 4 tiny holes Vs 2 small holes. Now given that Porsche seemingly just changed from one to the other over the course of the 3.4 production run with no other changes that I could find, I'm just going to run these new ones as replacements for two of my injectors and see what happens. Worst case I still have my two other originals, which did work fine but weren't in great condition.

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Yes I did notice that too. I'm going to message the seller and ask why the car was broken for spares. I'll also crack test it using a dye penetrant test kit I've got. I'm not particularly worried, it seems very uncommon for 3.2 heads to crack from what I've researched.

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Well if you get a recon kit for all 6 you'd have them all the same then. I can't remember off hand what they come as in that kit , I think i got mine from aptly named "Mr Injector UK" must be a franchise .. actually maybe it is.

Cheers for that Monty, just had a look at their website, found this kit which looks right: https://www.mrinjectoruk.co.uk/prod...ly-2000-before-fuel-injector-15mm-seals-kit-9 However, maybe the pictures aren't great, but that kit doesn't look to me like it would replace the nozzle with the 2/4 holes?

Yeah you're right, it's just the caps.

So are the nozzles replaceable or are they part of the body of the injector? I could take my old ones apart and swap over the parts? Also I've received a message from the seller I bought the head from saying that the car had a failed oil cooler which was apparently going to cost more to fix than it would cost to strip the car for parts. They only sell 986 / 996 parts and have very good feedback so while I'll still crack test the head, I'm not worried about it.

I don't think you can change anything on the injectors other than the parts in the kit. Those plastic covers (pintle caps) can be quite tricky to take off. One of mine bent king of deformed the nozzle slightly.

no the end caps with the holes in don't come off easy, it will damage them trying and if one works loose afterwards and get sucked in the bore, it would be really bad news. The kit consists of rubber seals,filters and plastic end caps.

Disaster has struck. Despite the eBay seller telling me otherwise, the new cylinder head is also cracked. @Hooner it seems you can predict the future. This is very annoying. Luckily it was bought through eBay so I've put in a return request and have received a free shipping label to send it back, but this still leaves me needing to find yet another head.

In some better news, my new (cheap) IMS Bearing has turned up, along with the snap ring from Monty and the upgraded centre bolt from Hooner. So I can at least get my IMS sorted this weekend, I'm borrowing the bearing puller to get the LN bearing out, but any tips for fitting the new one?

yes annoying but at least you got a no hassle refund .

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Yes fit a cable tie around the spring clip to act like a piston ring clamp when tapping the bearing in also put it in the freezer overnight. Like this

Do you have access all the way through an IMS? Asking as I don't know. If you do, I'd put a thread bar right through the shaft and new bearing and then a nut with a plate over the end and wind the nut up to pull the bearing in. If not, then you need some other way of pressing it in parallel to the core of the shaft. If you have a big lathe it's easy as you can grip the shaft in the check, then press the bearing in using the tailstock. EDIT: just realised you can't put a bar through cos of the spiggot (wadda dick I am!) With regards to assisting the bearing in, warm up the sprocket with a heat gun to increase the bore, make sure you put something slippy on the bearing to reduce any pick-up - I just usually spray WD40 on. Some will say freeze the bearing, but I'd never do that for risk of getting condensation inside it. EDIT: Tapping a bearing in is a last resort for me. It's a high precision engineered part of the engine.......not a 6" nail!!

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In normal situations all this is good advice, but there's no other way if the shaft is in the engine ,the bearing is full of grease so i don't think i'll get condensation in it i wrapped mine tight in cling film and it was ok. In this situation he has the shaft out of the car so he could press the bearing in and come to think of it , this would be the best thing to do if there's a press available. Dont for get to press the centre bolt into it first.

"In normal situations all this is good advice, but there's no other way if the shaft is in the engine." That's why I'd never recommend doing it in situ. Think Hartech made some special tools to ensure the shaft and bearing are held in place within the block whilst the bearing is then pressed in. I'd knock up something similar if I had no other option.

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Yep , it's possible to screw some longer flange bolts through the holes where the flange fastens to the casing , which presses the shaft up tight against the oil pump end and stops it moving and bouncing around while the deed is done. I think whoever is doing the job has a lot to do with the out come i've seen some horrific stuff

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I (finally) just got my c2.1 back from Hartech. Alex, I took your advice! The upgrade from 3.4 to 3.7 is worth every penny. And Nathan you’re doing an awesome job whatever you go with.

Some success today. Got the old IMS out without much trouble. The centre nut is in the freezer currently in preparation for installing it in the bearing later today. Then they'll both go in the freezer overnight and I'll hopefully be able to install it tomorrow. One question about the seals on the bearing, do I remove them on both sides or just the side facing out? I ask because the LN bearing that came out had no seal on the flange side but did have it if the shaft side.

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I removed both seals to let the oil run freely right through the bearing , i can only think someone else must have pulled the seal on the LN bearing after it had been originally fitted.

Personally I'd only pull the front one. Why would you want oil stuck in the shaft? Once in, can't get out.

Well the bearing that I took out only had one seal removed, and there was still plenty of oil inside the shaft. I think if oil got in there with the rear seal still on the bearing then I may as well remove both because what the rear seal will definitely do is stop the oil getting back out again whereas taking both out might give the oil a better chance at circulating through.

A bit more progress today as I wait for parts to arrive. Lots of wirebrushing and scrubbing so that I'll have nice clean parts to bolt back onto the rebuilt engine. A few before and afters as proof. Also some painting being done. I've wirebrushed, rust converted and etch primed my fuel rails and injectors so make them look nice and hopefully prevent them corroding any more.

Did some investigating into the fuel injector differences between the two types that the 3.4 engine uses. A page or so back I showed that I had found that the electrical specs of the two injectors were pretty much identical, and given that they also appear identical apart from their colour and part number, I decided to buy two used green 0280150470 injectors off eBay to replace two of my dark blue 0280150455 injectors which were quite rusty. And so they turned up and I was immediately proven wrong about my theory that the injectors were identical, as the nozzles were different. One had 2 small holes, the other had 4 tiny holes. So today, in order to decide whether I would still use the new ones or come up with a new plan, I put together a very basic injector test rig, consisting of a tyre valve stem courtesy of my local Kwik Fit, a spray can of brake cleaner, some crocodile clips, and a spare car battery. And once I worked out how to stop the valve stem popping off the injector and spraying brake cleaner in my face, it worked quite well. The pictures are poor due to them being screenshots of the videos I took, but you can see what you need to see. I would appreciate some input from others on this, but the spray pattern of the two different injectors look similar enough to me that I think I'm happy to the two different types together in my fuel rails.

Does anyone know if it's possible to test the chain tensioners somehow? They feel like the type of thing it would be sensible to replace but at the same time if mine are ok then I would be quite happy to save the £400 that 3 new ones will cost me.

A few updates since last week. My spare time this week has largely been spent in the garage armed with a wire brush and brake cleaner. My exhaust hanger brackets were, as usual, pretty crusty, but they turned out fairly decent with some use of the angle grinder and some high temp paint. Took some persuading to separate the cats from the manifold, but definitely worth the effort as my shiny new (Chinese) manifolds have turned up. These cost me £112 delivered from Alibaba, and much to my surprise, they seem very solid. I suspect the manifolds you see for sale for double this price or more are identical to the set I have received. Both my set of injectors and my second hand anti roll bar have come up quite nice after some rust treatment and yet more high temp paint. Gave the engine wiring loom a good clean, and glad I did because I found the earth lead for the injectors / coils (?) was pretty much falling off on its own. Sorted this with a new connector from a Halfords multipack.

And the most exciting news this week: My quite sizeable Design911 order has arrived. Still waiting for a smaller order of parts direct from Porsche, but once that turns up I will have everything I need to start putting my engine back together. Well apart from my case halves and a new cylinder head obviously....

Those Chinese manifolds are bob on.

I’d agree they’re all the same, just buy the cheapest which I think you’ve done. glad you found that earthing point..they all seem to go there

I’ve been watching this YouTube content covers some interesting engineering process. Thinking about companies that may be able to help fix / weld your existing cylinder head

I’ve only ever sent injectors out for cleaning & testing, I’ve never done it myself. They can have quite big differences in break pressure & flow stats even from new. If you’re going to all this work im sure it wouldn’t break the bank to get them tested properly, maybe Hartech would have a tried tested partner they could recommend for the work ? Great work, good to read your thread.

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Thanks. However having spoken to a few different places that said they could weld the crack in my cylinder head, I am very reluctant to go down that route. While it is certainly possible to weld the crack, there is no guarantee that the fix would last, and everyone I have spoken to about repairing it has advised that welding it would be a last resort. One place did recommend that a better repair option would be laser welding, which would be more accurate and longer lasting, but the cost of laser welding and machining afterwards would be pretty much the same cost as just buying a new head. I'm still intending to go down the modified 3.2 head route, which should be significantly cheaper if I can just find a head!

On another topic, I'm planning to do some work on the car itself this weekend while the engine is out. Going to replace the over gearbox brake line as well as any others that don't look great. New radiators and AC condensers too, as well as trying to clean out the main coolant pipes of intermix sludge while accessing is easier. Another thing I'd like to do if possible is sort out my engine bay insulation, which isn't awful at the moment but I don't want it to get worse. I see that a new insulation panel (99655671103) is around £300 which I'm definitely not prepared to pay. I'm thinking would I get away with covering my existing panel in some kind of heat resistant tape to prevent it from splitting and disintegrating any more?

Check the condition of those over engine aircon pipes, especially the low pressure side. Under the clamps is where they rot.

how about a self adhesive sheet material - similar to sound deadening but heat resistant........... https://www.soundinsulations.co.uk/...n-material-marine-hvac-engine-bay-car-1m-x-1m

If you can’t find a good used head welding repair might be the only option? which sides cracked? Wonder if they always crack the same side? This is on eBay. https://ebay.io/m/ACvdkD

It's the 1-3 side that's cracked, and from everything I've researched (which at this point is a lot), 99% of the time it's the 1-3 side that cracks. Something to do with that side running hotter and having larger coolant passages and therefore thinner wall thickness in the casting. I could be wrong about which side has bigger coolant passages, but either way the result is the same. Thanks for the link, but unfortunately that is a later 3.2 which is a 3 chain rather than the early 3.2 with 5 chains. The only 3.2 head that will fit a 3.4 engine is the M96.21, for the reasons I've just said. I may have some good news, but I will hold off until I can confirm it.

Interesting. Wernt the head castings the same hence the IMS shaft. Can you use a 4-6 head or is there machining drilling differences ? I hadn’t picked up the 3 chain difference on boxster, I knew it on 911, Every days a school day.

It could be different coolant passage size in the block that I'm thinking of? Not sure but I think I remember reading something about it. I suppose you might be able to use a 4-6 head but there's a significant number of machining differences that I could see. Chain tensioner location, chain guide mounting points, oil galleries, etc.

Lee from Hartech: View attachment AQPFByNAHIR9xxUSBPnut0dkTNyHGDJuoRL_l6BA1--cvXa-5PMvknTw2wkLIS8gTQiXIiqHq53RFYRfsXl2tcpQ7jSrXV...mp4

Very interesting, what he's saying about crack location is exactly what I've seen on both cracked heads that I've looked at. That method of pressure testing is cool to see too, I wonder what it's fixed to in order to force pressure out the top?

I can’t open that vid.

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How about this.

Another thing that occurred to me as I'm trying to plan ahead is the replacement of the small end bearings on the con rods. I hadn't actually done much research on them until now, and I'm not finding much information on them. I have ordered a set of them, and by the look of them it seems like they probably need to be pressed out and in, which is fine. However I have seen it mentioned on other forums for different engines that the new bearings would need to be bored out to match the wrist pins? They also suggest that the small end bearings are possibly not worth replacing unless they are significantly worn. Just wondering if anyone else has experience of replacing them on these engines.

From Lee Jenkins at Hartech:

Right well that's that answered then, thanks Alex. I better check mine this evening and hope that they're ok to reuse.

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No on both counts for me. I am close to IT illiterate though so it’s probably me

David Moore covered this recently on his YT reconditioning & balancing rods on the Ferrari engine, might make interesting viewing.

Had a look at my rods last night, they've still got the pistons on them so easy to feel if there's any play. Lucky for me, essentially zero play in them at all, only the side to side movement as they slide on the wrist pin. Hopefully Porsche will let me return the set of bearings I had already ordered.....

Time for another progress update. Spent the weekend on preparing the 4-6 head for reassembly, starting with the simply delightful task of drilling out two snapped exhaust manifold bolts. Luckily I was able to borrow a Stomski jig so while it was pretty tedious, it wasn't that bad. I also took the opportunity to chase the threads on all the other holes to hopefully make it all go back together nicely. Then fitted my new titanium exhaust studs, which should make sure that it'll be nice and easy to replace my Chinese manifolds when the time comes. Then moved on to cleaning up the mounting face of the head. Next up was to pull all the valves so I can fit new valve stem seals. Bought a cheap toolkit off Amazon which actually turned out to be pretty good, although I did have to resort to ratchet strapping the head to my table in order to get enough leverage... While the valves were out I decided I may as well lap them in, seemed silly not to do the extra step. Gave the valves a good clean with a wire wheel too. And there we have one head prepped and ready to be reassembled.

Did a bit more cleaning, just the throttle body and oil scavenge pumps to clean as they're the last external engine components to do. Glad I did the scavenge pumps as one of them looked like it may have spent some time in the sea.

Was it robbed from my car?

And finally, the good news I'm sure you've all been waiting to hear: I have got my hands on a crack-free cylinder head. It came off a Boxster 3.2 head that had suffered from a cracked cylinder 4, which caused cylinder 4 to fill with coolant and the owner of the car to believe that it was a cracked head. Lucky for me, the seller showed me pictures of the engine as they were taking it apart, and there was absolutely no sign of any intermix. They were very helpful and cleaned the oil from the surface of the cylinder head in order to send me detailed pictures of the areas where cracks usually appear. I was happy with what I saw, so I agreed to buy it. It arrived today, so after work I gave it another good clean and then used a 3 stage dye penetrant test kit to double check for any cracks. It appears to be all clear, so happy days.

Yay!!!!!!!!

Next steps are to work out exactly what machining I need to do in order to convert this 3.2 head to a 3.4. I got some pictures of the two heads side by side so you can see the differences in the bowl around the valves. I plan to 3D model a template of the 3.4 head which I can attach to the 3.2 head to mark out the areas I need to grind away. I have also acquired a CC measuring kit so I can get as close as possible to the same capacity. Picture of the valves from my other 3.4 head sitting on the valves of the 3.2 head show that the valves are identical in size.

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Very much agreed

Great news on finding a head! It’s hard to tell because of the debris on the 3.4 head but the combustion shape appears to wrap round the exhaust valve slightly more on the 3.2. Interesting. And if you left it as it is? Now we’re into the realms of thermodynamics? And I’m out of my depth. Porsche changed it for a reason ..

Yes, the 3.2 head has more material surrounding the valves. I assume it's to do with the smaller bore diameter on the 3.2, I guess the gases need to flow differently? I also don't quite understand why the shape is different but as long as I match it to my original head I think I'll be OK. I've drawn this diagram using overlaid images of both heads to show the difference in shape.

Wow! Impressive, feel like being at school! An interesting one that is

Definitely worthwhile cleaning up the exhaust manifold mating surface too. Thanks for sharing this great to follow along.

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Great work

More updates incoming. Over the weekend I spent some time working on the car itself for once. First job was to prepare for the next task by fitting stainless caliper bleed nipples. Anticipated some issues doing this as the existing fittings were looking pretty crusty but to my surprise it went pretty smoothly. Managed to replace all 8 bleed nipples with no real issues. Next up was to replace the flexi lines all round with some Goodridge braided lines as, again, the existing lines didn't look great and had been mentioned in the last MOT. This got a bit more involved as I ended up having to make up some new flexi to caliper hard lines due to the destructive nature of removing the old flexi line. End result was new flexi lines and flexi to caliper lines on all 4 corners. And now for the main event. Replacing the over gearbox brake line, as this had also been mentioned in the last MOT. Had to chop the original one in half to get it out, then did my best to estimate the length I'd need to make the new one. What followed was several hours of choice words and struggling, but the end result was a new brake line, which (roughly) follows the original routing, is held securely, and doesn't touch any other components. I did have to make it in two parts and join them in the centre, but I couldn't see any other way to do it without doing a lot more disassembly than I had time for. I'll bleed the brakes before the engine goes back in so I can make sure the joint doesn't leak. The next task was one I really wasn't looking forward to. The last thing I want to do when I put the engine back in is to start it up and immediately fill the cooling system with leftover intermix. So I needed to try and flush out the cooling system on the car before the engine goes back in. Conveniently, the lift I was borrowing is both outdoors, and has a pressure washer available nearby. So I came up with a plan. I 3D printed some rubber bungs for the coolant lines, which I fitted after removing the radiators. I designed one of the bungs to fit onto the nozzle of the pressure washer, and placed buckets under the other end of the coolant lines. I then spent several hours flushing water through the coolant lines. I flushed each line (4 main lines in total) through 5 times. 3 times 'backwards' - pressure washer at the radiator end, bucket in the engine bay, and twice forwards (the opposite of backwards). During the whole process I had all the openings apart from the two I was flushing through blocked off, as both lower radiator hoses join to just one pipe which ends in the engine bay, and the same for the uppers. I also flushed through the breather hose which connects from the top of the coolant bottle to the top of the radiators, as well as the heater piping. I flushed through about 20 20 litre buckets worth in total, which seemed to do the trick. The images below show the first bucket I flushed through, Vs the last bucket. I have no doubt that I will still need to flush the system a couple of times once the car is back up and running, but it will certainly be a lot better than it was. And last task on the car for the weekend was new radiators and AC condensers. It didn't make any sense to try flushing through the original radiators given the condition they were in, plus they were off the car anyway. A nice satisfying job to finish off cleaning up the cooling system. And lastly, a new coolant bottle. Surprising how easy it is when there's no engine in the way...

Excellent Nathan!! Looking great

Great work ! Keeping another one alive .

Impressive stuff great write up.

Today I got stuck into modifying my 3.2 cylinder head to convert it for use on my 3.4 engine. The last time I mentioned it I posted a diagram showing the difference in combustion chamber shape between the 3.2 and 3.4 heads. So my first task before I did any modifying was to take measurements of the capacities of both heads. I did this with some very sophisticated equipment, consisting of a piece of acrylic with a hole in it and a 60ml syringe. For both heads I simply smeared some grease around the edge of the acrylic and pressed it down onto the head to create a seal. I then filled the syringe to the 50ml line with water, and slowly filled the combustion chamber on the head through the hole in the perspex. Once there were no air pockets and the water was just reaching the top of the hole, I took the measurement of how much water was left in the syringe. And my results were as follows: 3.4 head - 36.5ml capacity 3.2 head - 34ml capacity These measurements line up with the roughly 3cc difference explained in this thread, so that was nice to see. Next task was to strip the valves out of the 3.2 head, as I didn't want to risk damaging them during my modifications to the combustion chamber. I bought the tool to do it for about £20 off Amazon, and I was very impressed for the price. While I was at it I also stripped 4 valves from the 3.4 head too as sacrificial valves for the modifying process. In order to accurately reshape the combustion chamber of the 3.2 head, I designed and 3D printed a simple jig to allow me to mark out the exact shape of the 3.4 head on the 3.2 head. The pictures below show the jig fitted to both heads, with the 4 locating prongs fitted into the holes for the head bolts. With the jig fitted to the 3.2 head, I used some layout fluid (black Sharpie) and a scribe (old exacto knife) to mark my line that I would need to work to. I had hoped to be able to leave my jig in position while I worked on the head, but I realised it would get in the way too much. So instead I used the old headgasket and paper towel to protect the areas I wasn't working on from getting covered in metal shavings. And then I just got stuck in with the die grinder. It was actually a lot easier than I expected, if slightly terrifying at first. I did the rough shaping and the bulk of the material removal with a ball shaped grinding bit, and then switched to a sanding wheel and hand sanding for the final finishing. Rinse and repeat for the other two cylinders. Very happy with how this turned out. When I finished machining each cylinder I repeated my initial measuring process to check that I had removed the right amount of material. On all 3 I got within 0.5ml of the original 3.4 head, which should be absolutely fine. Next thing that needed modifying to convert to a 3.4 head was to add the threaded holes for the exhaust backbox hangers. 5 new holes were needed, two on the exhaust side and 3 on the intake side. All M8 X 1.25, the only issue was getting them centred and at the right angle. Once again my 3D printer came in handy, as I designed two more jigs that would hold the drill bit guides that come in the Stomski exhaust manifold jig kit, and keep them centred and perpendicular to the surface. I also had to drill and tap 4 new M6 holes to mount the 3.4 intake manifold, as it seems that the Boxster intake manifold must be a different design. I'd had enough of designing jigs at this point so I just used the old gasket to mark the centres of the holes, then drilled and tapped them by hand. And lastly, as expected, I had to drill and tap 5 of the 6 exhaust manifold bolts, then replace them with titanium studs. And with that, I have now converted a 3.2 head to a 3.4 head. Aside from some part numbers and some extra holes around the intake manifold, it is identical to a 3.4 head. Over the weekend I need to clean and lap the valves, and then reassemble with new valve stem seals.

Quality bit of work there mate, well done it looks very good

Great work there enjoying reading the updates, I’ve done a few things over the years but I’m yet to take a die grinder to a combustion chamber !

Brilliant stuff. I think this will become a thing to do in the future with the lack of cylinder heads and old ones cracking but this shows it can be done at home with the right tools. Awesome.

Excellent job. The Allan Millyard lard school of fettling.

Thanks everyone for the kind words. To be fair, I've never done anything like this either, I just did lots of research and prep work to give myself the best chance of it working out. I also feel like doing this conversion will become something more common and I'd be happy to supply my set of jigs if anyone is interested, but maybe we should wait until I have it running to make a final judgement!

A bit more work done on the car itself over the weekend. My engine bay sound deadening pad was like most, cracking and sagging down. Seeing the price of a new one and knowing about all the pipework that needs to be moved to replace it, I came up with what will hopefully be a decent solution. First I used some high temp contact adhesive to glue the pad back up on the firewall. Then I gave it a good scrub with degreaser and brake cleaner, before I covered it with heat resistant tape. This stuff is very sticky and resistant up to 150 degrees so I'm hoping it will last a while. While I was in there I also cleaned and painted the rusty area around the seam above the gearbox.

The next task of the weekend was to start doing some reassembly. Starting off with putting the cylinder heads back together. I fitted new valve stem seals, then refitted the valves and springs. I did unfortunately damage one of the stem seals when I was fitting them so I'll have to wait a couple of days to fully finish off the heads. An interesting detail I noticed while cleaning up the valves was that the Boxster valves (left) seem to have an odd pattern on them that I assume is to do with the machining / finishing process when they were made, as all 6 Boxster intake valves have the same pattern. The 911 valves don't have this pattern, but they do have a '98 production date etched on them where the Boxster ones have an '01 date, so I wonder if it is simply a slight change based on production dates rather than anything model specific. I decided I would be better off reusing the Boxster valves rather than swapping in my old valves from the cracked head, just because I wanted to make sure any wear in the valve guides would match the valves. I did swap to the valve springs from the cracked head as they had different numbers printed on them compared to the Boxster springs, just in case there was any difference.

It has been a very busy month with not much time for updating this thread, but I have now made significant progress so it is time for a write up. Following on from reassembling the heads, my next task was to put together the crank assembly. My crankshaft was thankfully in very good condition after 126000 miles so this was just a case of fitting new bearings and bolting it together with new bolts. Torqued everything to spec (25Nm + 90 degrees I believe) and then marked with a paint pen so I couldn't second guess if I'd torqued them or not. Next up was to strip down the piston + rod assemblies to fit new bearings and ARP rod bolts. The ARP upgrade wasn't strictly necessary but I read too many forum posts about broken rod bolts and got scared. Then the rods for 4,5,6 have to be installed on the crank ladder before it goes back into the engine. I also replaced the IMS chain wear pad and guide rail as it was pretty badly worn. All new chains were also fitted because why wouldn't you. As I was still waiting for my case halves from Hartech I continued rebuilding subassemblies and refreshed the oil pump with a good clean, new seal and new updated oil pressure relief spring and piston. Cams were next with new chains and Variocam pads. This was quite fiddly and not having the correct tool for compressing the Variocam actuator didn't help, but was certainly worth doing judging by the state of the old pads. One thing I later found out about the timing of the cams relative to each other is that you can't set both sides up exactly the same. Both sides need to have the dots on the cams 8 chain links apart, but you need to have the notch on the exhaust cam facing in the direction it needs to be in for the timing procedure when you set that. I did both sets of cams in one go, and did both sets with the notch facing up, which I later found messed up the timing of bank 2 and I had to redo the cam to cam timing. And at last, after what felt like a very long time but was only about 6 weeks, I got the email from Hartech to say that my cases were ready. I drove up to collect them on a Monday morning before work so that I could crack on with putting it all back together ASAP. For anyone who is wondering, as although their work is excellent, their website isn't, what you receive for £5040 is: 6x Nikasil liners at original 3.4 capacity, 6x Capricorn updated pistons, 6x wrist pins, 12x wrist pin clips, full set of piston rings, gapped and ready to install, a low temp thermostat and a bottle of assembly lube. Not sure about what anyone else thinks but I think it's actually a very reasonable price for everything that you receive, especially considering the reputation they have. And as mentioned, with my case halves home, I got stuck in to putting it all back together. First step was to learn from my mistake when taking the engine apart, and make sure that the bank 1 case half is bolted to at least 3 points on the engine stand, as things get a bit wobbly with only two. And with the crank ladder ready to go, it was a case of drop it into place and get ready to install the pistons. As I saw in several other threads, it is definitely worth having another person to help with this step as the crank ladder is rather heavy, however as I didn't, I can confirm that it is possible to do by yourself, I just don't recommend it. Assembling the rods and pistons is relatively straightforward, and it gave me an opportunity to practice installing the dreaded wrist pin circlips. In theory this step is simple with the correct tools, but as I found out it only takes a very tiny misalignment for the circlips to end up seated on the outside of the groove that they're supposed to sit in. This did not make me feel any better about installing the other bank of pistons...... But anyway, things went smoothly on this side of things, and I got the pistons on bank 1 installed without issue.

Moving on (nervously) to bank 2. I deployed Porsche special tool 457383 to hold one of the chains up so that I could place the bank 2 case half down without ruining the carefully applied sealant, not forgetting to install the two hard rubber gaskets around the coolant passages beforehand. Once the case halves are fitted together it was then a bit of a rush to get all 30 or so bolts in and tightened up before the sealant goes off. After checking that the case halves had seated properly and running out of other things to procrastinate on, I started the process of installing the bank 2 pistons. This starts with using one of the special tools to line up the rods in the centre of the bores, and then fitting piston No. 6 into it's bore. With the centring dowel still in place, I tapped the piston down until it touches the dowel, then pulled the dowel out of cylinder 6, and continued tapping the piston down until the wrist pin hole lines up with the con rod. The centring dowel is tapered so if the piston is slightly out of line you can tap the dowel in to line it up properly. Before inserting the piston, the circlip on the far side was installed so the next step is to use another special tool to fit the wrist pin. This involves a load of assembly lube on the wrist pin, followed by hoping that the con rod hasn't tilted away from the centre of the bore, and pushing the wrist pin home. A borescope is very handy at this stage to check that the pin has seated all the way into the piston. Then, in order to check that the pin has actually gone through both the piston and the rod, I turned the crank a couple of turns to make sure that the piston got dragged both up and down. I'm not really sure what you'd do if it turned out that the pin had missed the rod, but luckily I didn't have to solve that particular issue. It was now time for the scary bit. With a circlip loaded into the end of the special tool, and after triple checking everything that could possibly be checked, I went for it. After a couple of goes to make sure that the tip of the tool was seated inside the hole in the piston, and very firmly gripping the tool the make sure it stayed there, I gave the end of the tool a good smack. Then very nervously pulled the tool out of the piston, expecting to hear the ping of a circlip finding a new home deep inside the engine, however there was nothing. A check with the borescope confirmed that all was well, the circlip seated perfectly in the piston. The next two pistons went just as smoothly, with the biggest difficulty being a floppy con rod not wanting to stay centred where I needed it. In hindsight, installing the circlip with a piston in the cylinder is almost easier than installing them while holding a piston on the bench as the holes in the case half pretty much keep the installation tool in position, and the piston can't move or slip to cause the tool to misalign. Anyway, that was the most difficult part complete. Next up I installed the 'front console' in order to support the end of the IMS shaft, along with the waterpump and the plug for the circlip installation hole. Then I refitted the oil pickup and what I think are air / oil separators in the sump.

The heads got bolted on next, looking very nice all cleaned up with new gaskets. I also fitted new chain guides, and in the process had a bit of an incident with one of the bolts which was very annoying and took a couple of hours and yet another 3D printed jig to sort out. The tappet chests and new tappets were next, followed by the cams with the new chains and wear pads. This was a bit of a faff, and I had to fit and remove the cams a few times until I realised that you need to keep tension off the Variocam actuator until the cams are seated and bolted down, otherwise it is very difficult to get them to sit into the bearings. Once they're seated, the two bearing caps can be fitted, the hold down tool at the end of the cams fitted, and the two hold down tools in the middle removed in order to fit the cam cover. One last step before starting the timing procedure is to fit the 3 chain tensioners. I reused all of mine and just fitted new O rings, as they all seemed perfectly OK. The timing procedure is pretty straightforward when you've got the right tools. The crankshaft gets locked at TDC for cylinder 1, the timing sprocket bolts on the exhaust cam get loosened, and then the cam timing tool gets bolted into position. You rotate the arm of the tool until the diamond-shaped bolt slots nicely into the recess where the end of the cam is. This tell you that the cams are positioned as they need to be relative to cylinder 1, so then you can tighten up the bolts on the timing sprocket and turn the engine over 360 degrees to time the other bank using the exact same process. One thing to note is that when the manual mentions that the single notch in the end of the intake cam is supposed to be pointing up/down (depending on which bank), it does not have to be pointing exactly up/down, it does point slightly off to the side. When I had both banks timed and the timing sprockets tightened, I then turned the engine over 10 or so times, checking each bank every other turn with the timing tool to make sure it still lined up. Interestingly, this was the last thing I did that day, and when I came back to it the following morning, I repeated my steps from the day before and found that although the timing had been absolutely perfect after 10 turns the day before, it was now slightly out. After triple checking the tool and everything else, I ended up loosening off the sprocket bolts to adjust the timing back into spec. It wasn't out by much at all, but enough for me to notice, so I have to assume that maybe the new chains stretched very slightly overnight as the tensioners were fitted putting pressure on them? Either way, that was the engine 'long block' fully assembled and timed.

First post from a lurker who is also rebuilding a 3.4l M96.01 after a spun big end bearing on track. I believe that the reason for your observation lies in the chain tensioner, if you have filled it with oil just prior to fitting it and timing the cams that is. Over night the oil has leaked away into the oil gallery that supplies it during operation and now the valve spring forces rotate the exhaust cam ever so slightly as the chain is no longer held under as much tension by the tensioner as when it had oil in it. OTOH the orifice in the tensioner is quite big at ~1mm and the oil inside the tensioner probably leaks away within a minute, leaving you with just the force of the spring inside the tensioner to tighten the chain during cam timing anyway... Long story short, if you filled the tensioner with oil just prior to timing you might want to fill it again and see if the timing tool now slots into the bore of the cam again. HTH .

That explanation does make sense, however I didn't fill the tensioners with oil before installing them as it felt like the spring inside them was providing plenty of force to tension the chains well enough.

After checking the timing a few more times I started fitting the seals and accessory parts. New cam end caps were lightly tapped into place, followed by the spark plug tubes fitted with new O rings. The oil scavenge pumps were next, being careful to line them up properly. Then the metal coolant lines and large rubber hoses, after making sure there was no more intermix residue inside them. I refitted the oil cooler that came on the car as it had been replaced less than 50 miles before the car was parked up as the previous owner's last hope for fixing the intermix issue cheaply.... I bolted on the lower intake manifolds and was very relieved to find that my DIY drilled mounting holes in the bank 1 cylinder head lined up perfectly. Then new spark plugs and coil packs, along with some spacers for the head shields. And then a fun bit: new exhaust manifolds. These were £100 from Alibaba, and I have to say I am very impressed. No issues with fitment, they seem decently solid, and if it comes to it, I've got titanium studs and copper nuts fitted now so replacing them shouldn't be an issue. A new Genuine AOS, Bosch starter motor, refreshed exhaust backbox brackets, new oil filler neck and Variocam solenoid seals all got fitted, along with the alternator, A/C compressor (less than a year old) and power steering pump. Following on from the satisfaction of fitting a load of new parts, I had the less fun job of figuring out how the wiring loom is supposed to be routed. All I'll say is that I'm very glad I took a load of pictures as I was taking the engine apart two months ago. Then even more tubes and hoses as I fitted the fuel rails, vacuum lines, and AOS hoses. And lastly to finish up this particular day of work, I cleaned up the intake manifold and fitted new seals. Intake manifold bolted on along with the throttle body. New accessory belt and new pulleys to go with it, and a 24mm socket holding the belt in place as I was still waiting for the last new pulley to arrive. While I waited for it I bolted up the engine mount bracket and then fitted the original cats with new stainless bolts and copper nuts. And with that, the engine was pretty much complete. Some small jobs left to do, like torquing the IMS centre bolt and fitting the new RMS, but done until the engine comes off the engine stand.

About a week later it was go time. Got the engine off the stand and onto an engine table in order to fit the RMS seal. Had a bit of a full circle moment here as I used a 3D printed tool that I had designed about 7 years ago for my dad's business as he had a customer who needed the seal replaced, when I never thought I would be in a position to be needing the tool for myself. Then bolted up the (new) clutch and flywheel, and with a bit of a struggle got the engine loaded into the back of the van. A similar struggle at the other end to get it back out, then an hour or so of bolting on the gearbox (with new Powerflex bushing inserts) and backboxes, and we were ready to get it back in the car. And about 5 hours later, it was in. Fluids topped up, coolant system filled with a mixture of water and bio-degreaser (what Hartech recommended I use) to try and clear out the last of the intermix residue, and it was ready to try a first start. I pulled the fuel pump fuse initially to allow some oil to circulate before going for it, and with the fuse back in, it fired up no problem after a couple of tries. For the first few minutes a couple of the tappets were quite noisy as the thick assembly oil was not yet flushed out, but after about 10 minutes of running and some revs they quieted down. Very relieved that it was running nicely, my next objective was to get it up to temperature to allow the degreaser to dissolve any oil left in the cooling system, before draining the coolant and filling it with plain water to flush the degreaser out. I did this 3 times in the end, twice with degreaser and water, then the last flush with just water before I filled it with OAT coolant. The pressure bleeder that I had wasn't working properly, so I resorted to lifting the back of the car in order to hopefully allow any bubbles to rise to the top where the coolant reservoir was. I then spent the next two days (it only took one to get the engine in and running) fitting new front discs and pads and bleeding the brakes and clutch. I was doing this on my own so it was a bit of a pain in the arse, but the end result was that on the Sunday afternoon (we took the engine off the stand in my garage on Friday morning) I drove the car properly for the first time. Luckily for me, there is a half mile private driveway at the unit where the lift I used is, so I was able to do a couple of miles up and down the driveway to get it up to temperature and test the brakes and clutch properly. Driving it also helped to burp out more air from the cooling system so every few laps I had to stop to top up the coolant. All that was left was to get the front bumper and engine lid back on and check it over for an MOT the next week. A very successful weekend and the ideal ending to two months of work.

Unfortunately, things are never that simple.... During my check over after getting things up to temperature and using some of the revs, I spotted not one, not two, but three oil leaks. Very annoying, but I had expected something to go wrong at some point, as these things usually do. Two of the leaks are coming from each of the scavenge pumps, I think from one of the bolts on each pump, so that's clearly my mistake for not using enough sealant on the bolts. I'm planning to remove the bolts this weekend and put more sealant on them, and I'm hoping I'll have enough space to do this on bank 1 where the pump faces the subframe. The other leak is a bit more of an issue, as it's coming from the snout of the oil pump where it fits into the engine case and support the other end of the IMS. Very very annoying but there's no other option to sort it other than to pull the oil pump off again and replace the O rings. I've already discussed this in this thread but in order to remove the oil pump the crank and cams need to be locked and the chain tensioners removed. This is also a job I have planned for this weekend so I will hopefully be back with an update in a few days.

Nothing like turning the key for the first time on an engine you built yourself ! Very frustrating to get the leaks, hopefully an easy fix

Just spent a couple of hours trying to sort out the two leaks from the scavenge pumps. I was pretty sure that it was coming from the bolts that hold them into the head, so I removed each bolt one by one and put some more sealant on the threads and under the head of the bolt. Unfortunately both sides are still leaking, so I now have to assume that it must be the O rings. I had ordered some anyway so I'll have to undo my work tomorrow to fit the new O rings. Wondering if using some sealant on the O ring might be a good idea?

I use sealant on the O rings and they dont leak.

I wouldn't use sealant with O rings. O rings rely on clean surfaces. Maybe a bit of engine oil as lube but that's all.

Just my experience from a non automotive but a precision engineering background.

Well I suppose I don't mean sealant on the O rings as such, I was thinking a bit of sealant on the mating face next to the O ring would help. Parts of the issue is that I'm pretty sure on bank 1 I won't actually be able to remove the scavenge pump completely, or even 2 of the 4 bolts as it's just too close to the subframe on that side. I'm planning to pull the pump out as far as I can on that side so I can check the O ring and mating faces, and hopefully apply some sealant around it. Unless I can actually remove all 4 bolts I won't even be able to replace the O ring.

My experience no you cant get it all the way out bank one it hits the subframe. I wouldn’t expect it to leak from the bolts ? Assume you put new o rings on?

Yes new O rings when I rebuilt the engine. The bolts are through holes and go through into the inside of the head, the manual says to use 'microencapsulated' bolts which as far as I can tell just means use sealant on the bolts. It really did look like this is where the leaks are coming from but with the sealant I put on the bolts today there is no way it's still leaking from them so it has to be the O ring

I fitted new O rings (the big ones) but didn't put anything on the bolts , I wasn't aware they were exposed to oil in the threads. No leaks so far. Those scavenge pumps are made in England and they take a right beating with corrosion , I wonder if they're a slightly different type of alloy to the Porsche block and acting a bit like an anode.

I put new o ring re used bolts no sealant on anything all ok My pump looks like it was bolted to the titanic..

You can check my variocam thread for some tips but unfortunately you need to pull the cam cover to remove the scavenge pump on bank 1/left bank. Man I hope my pumps don't leak!

Could be the big o rings are not the correct size, were they genuine?

What detergent flush did you use to clear the latte? (Similar issue on son’s C2 $hitroën)

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I used this stuff, you can get it in Halfords. I flushed the system as much as possible with just water first.

I read a while ago about the negative effect the oil ingress degreaser etc can have on all the rubber coolant hoses, I don’t know if Hartech mentioned it in your dealings with them? Obviously if original they’re knocking on the doors of 30 years old now anyway. Maybe something to watch. A couple of mine look pretty dreadful well overdue replacement.

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I've seen it mentioned a few times about leaving oil in the coolant lines causing damage, but after all the cleaning and flushing that I did I can't see any signs of damage on mine. I think that could be the reason Hartech specifically told me to use a bio -degreaser, possibly less aggressive? This is the stuff they actually recommended, but I couldn't get any in time so I used the stuff I mentioned a few messages back from Halfords, labelled as a biodegradable degreaser, which sounded close enough to me. And it seems to have done a pretty good job as I haven't seen any oil residue in my coolant bottle so far.

Update time. Some good news and some bad news. The good news: the car is now road legal with an MOT passed with no advisories. I did let the mechanic know that I was aware of the oil leak and in the process of fixing it, but it also wasn't a very big leak so he didn't mention it. The bad news is that I have only had a slight success in fixing the oil leaks. To try and sort the leak I thought was coming from the oil pump snout, I followed the steps I mentioned in this thread to remove the oil pump with the engine in. In short: remove power steering reservoir, AC pump, lock crank and cams at TDC, remove chain tensioners (all 3), remove bumper + cats, support engine from below, unbolt from engine mounts, remove engine cradle bracket, remove oil pump, replace O rings + gaskets, reassemble and check timing. There didn't appear to be anything wrong with the old (new) seals or the mating surfaces, so I also used some sealant in between the two O rings. It was a little bit of a struggle refitting the oil pump even with the tensioners out, but I managed in the end by using an 8mm allen key to guide the end of the IMS shaft into the pump. The rest of the reassembly was pretty straightforward, and I turned the engine over by hand a couple of times before starting it up just to check that everything was still OK. Then I turned my attention to the two other smaller leaks from each of the scavenge pumps. When I first noticed these leaks, I thought that it was the bolts holding them into the head that were leaking, so I removed each bolt one by one to put more sealant on them before putting them back in. I went for a half hour drive after doing this (to the MOT centre), where I checked on the leaks to find that they were still leaking. On closer inspection, it seemed that on the bank 2 pump, the leak was coming from one of the inner bolts that holds the 2 parts of the pump together. I had taken this pump apart for cleaning during the rebuild, not realising that these bolts needed sealant too. So I removed the bolt that the leak was coming from, added some sealant and reinstalled. The bank 1 pump seemed to have a similar issue, as I had loosened one of the inner bolts during the rebuild before realising that trying to get them all undone would be a bad idea. However, because of how close this side is to the subframe, removing the inner bolt that seemed to be leaking was a lot more involved. I found that by removing all 4 of the bolts holding the pump into the head, pulling out and rotating the pump about 90 degrees, I could get all 4 bolts out and get a socket onto the bolt that I thought was leaking. I did the same resealing with this bolt as I had on the other side, and as I had all 4 bolts out I replaced the large O ring on the pump while I was there. I then added some sealant around the bolt holes before reassembling.

Having (thought) I fixed the leaks, I did another oil change (now about 90 miles on the engine), before heading off to the Peak District for the weekend. While the car drives quite well and the engine definitely works well, 2 of the 3 oil leaks remain. The leak I thought was the oil pump is still there and no better than before, and the bank 1 scavenge pump still seems to be weeping oil around the edges. Having done some more research on the oil pump leak, including an email to Hartech, it seems like the more likely cause for the leak is the non-Genuine front crank seal. Hartech say that this area of the engine is a pain when it comes to oil leaks, and that they've had lots of problems with leaks from the front crank seal over the years and they only fit Genuine Porsche seals. This is very annoying as replacing this seal is a lot less work than removing the oil pump, but oh well. I'll remove the crank pulley at some point this week to see if it looks like the seal is leaking, as I'm still a bit unsure about it given that I would have expected to notice the oil coming from higher up when I had the oil pump off. The other leak that is still present is from the bank 1 scavenge pump, I think I'll pull this out slightly so I can put some sealant on the O ring itself as the leak now seems to be coming from the outer edges of the pump. One other thing I noticed on my travels is that the temperature gauge seems to vary quite a lot. On motorways and faster roads it sits quite happily at 80 degrees, but on roads with more speeding up and slowing down, or sitting in slower traffic it gets up to around 90 maybe 95 occasionally. I mentioned this to Hartech too as I have their low temp thermostat fitted, and they say that these temperatures are fine. I'd be interested in what other think, as I was under the impression that it shouldn't really move away from the 80 degree mark if all is healthy.

When in traffic it's pretty standard for the car to get up to about 95 degrees before the fans kick in so the temperature variation sounds pretty normal to me. Good luck resolving the oil leaks, it's a weight off for me that they are (mainly) coming from the inner bolts. There are some o-ring sealants you can buy which might improve the sealing abilities...

Mine is just like that since Hartech rebuilt it (and also fit a LTT). sits at 80 all day whilst steady in motion. get to traffic jams or giving it beans and it's up in the 90s straight away. Don't worry about that. Before the rebuild it was always hovering around 90.

Glad you got it running and driving, hope you’re enjoying it. Real pain about the leaks, hopefully you get to the bottom of it.

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Same temps here, original engine 90k, it's normal behaviour.

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I'm cautiously optimistic about sorting the main oil leak with a new front crank seal, but saying that I'm yet to get the crank pulley off to take a look at the seal. I am enjoying having it back on the road, but at the moment I still find myself slightly anxious driving it as I'm not yet used to all the various noises and characteristics of the car, along with the minor issues it does still have. The car seems to run absolutely fine, and certainly revs nicely and has plenty of power, but there are some noises and things which make me think that there are still more issues to be sorted out before I can fully enjoy driving it. The whine at lower revs from what I assume is the auxiliary belt is slightly off-putting, but it appears to be normal from what I've found online. There's also a few noises which sound like gearbox / drivetrain to me, such as a whine which can be felt though the gearstick when decelerating, and a rhythmic sort of soft clunking when cornering which I would assume to be CV joint related but also sort of feels like it's coming from the front end. The central locking is also acting up, it won't unlock remotely with either key, and when unlocked with the key in the door the unlock button on the dash won't work until after the car auto-locks when I drive a few metres. The driver's window also has issues with dropping when the door is opened so I need to look into which of the micro-switches is dodgy. So nothing that actually stops me from driving the car, but enough things that I would prefer to sort out in order to enjoy the car more.

Mine whines at low revs since my rebuild and peaks at 2400rpm where it's almost a whistle, then disappears above that. I took it back to Hartech 2 days after collection and they said it was fine.

Was thinking about your oil leaks today, is it both heads or specific to the Boxster head side you replaced? I wonder if there’s a subtle difference in scavenge pump sizes fitment ? Assuming you used the original 996 pump ?

That's a very good point, the leak I managed to fix is on Bank 2 which is the original head, the one that is still leaking slightly is Bank 1 which is now the modified Boxster head. And yes I used both of my original scavenge pumps. I'm pretty confident that there isn't different pumps for a 3.2 vs a 3.4 but I will do a few more checks. What is more likely is that any pitting or corrosion around the mating surfaces would still match up on Bank 2 where the original head and pump pair were refitted, but Bank 1 has mismatched parts so any corrosion might be leaving gaps or preventing the O ring being compressed fully.

The O-ring is a face contact so even if the scavenge pumps were different diameters it wouldn't make any difference from a sealing point of view. Most likely is that the face is corroded slightly as OP says above. I would suggest a small smear of sealant on the face would do the trick, alternatively there are some O-ring sealant promoters out there like loctite mr5923 (I think)

Well serves me right for being optimistic. Pulled the crank pulley off for a look at the seal this evening and it is bone dry. No sign of oil running down towards the sump or anything around the edge of the seal. Looking back at the picture of the engine with the oil pump removed I cannot see anywhere else that oil could be coming from in this area other than the oil pump snout, which I have already replaced the O rings on. There was no sign of oil coming from between the case halves or from the oil pump cover. Thoroughly confused now.

Could it be the cam plug above the oil pump? Normally you should not need sealant on any joint with o-rings. If you do, something else is amiss.

Regarding the scavenge pump oil leaks, when i refitted mine I recall those large O rings being quite loose and easily slipping out of position. The groove they sit in is shallow. Someone on YT, could be Jake Raby, recommended using a few small dabs of sealant just to hold them in position until the pump was tightened down. Seemed to work for me, no leaks. Could be yours moved and got pinched.

I've been researching this issue I'm having with the leak from the main oil pump, but not really finding anything significant that could be a definite cause for the leak. I put up a post on a Hartech engine builder's Facebook group with an explanation of my problem, and have received the following suggestions: Oil pump housing is cracked from removal - didn't see any cracks when I last removed the pump and can't see any in my pictures Case halves are leaking from the join - can see excess sealant squeezed out from the join around the oil pump hole so very doubtful that this is the issue. Leak is from somewhere else - always possible but I can see oil on the oil pump snout when I look up under the car, can't see how oil would travel up to this point and it isn't leaking from the crank seal above. So with all this considered, I've bought another oil pump (second hand) that I'll crack test before fitting. I've also ordered another round of new seals - new O rings for pump (x2), 2x gaskets for the coolant passage, and the oil pump cover seal. I got some advice on my Facebook post to loosen off the two case half bolts that go either side of the oil pump hole to give the O rings a better chance of staying in shape as I push the oil pump into position, so I suppose I'll try that while I'm at it. Then it was also suggested to lubricate the O rings and hole, again to help the O rings stay in shape, but also to use some sealant on the seals? I assume that for the sealant to bond correctly it would be needing to bond to a clean surface which a lubricated surface wouldn't be? I'm planning to try and sort this (again) this weekend, so just trying to consider everything before I start.

Can you point to the exact place the oil is leaking from on the oil pump housing? I'm not too clear where you said it was.

It appears to be leaking from the back of the oil pump where it has the snout which pushes into the engine casing and supports the end of the IMS shaft. If I lie under the car and look up at the back of the oil pump in the gap between the pump housing and engine casing I can see oil gathering on the bottom of the pump snout.

get some slightly bigger o-rings, there is a company on ebay called selo who can make o-rings to what ever size you need. Looking at your pic there is the middle one too thin?

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Great spot and attention to detail

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Could be a good idea, they're supposed to be the same size as the Genuine parts though. Any idea how long it takes for custom sizes? 29.1mm x 2.55mm is the factory size

Quotes source post: 2831051

not too long i don't think, give them a ring. Selo source Ltd unit 2f spa fields ind est Hudderesfield.

How about 10 for £5.75 FKM O-ring 29.1 x 2.55mm (OD 34.2mm) 80 Shore A [10 Pieces] This O-ring has a 29.1 mm internal diameter and a 2.55 mm thick cord. FKM is a high performance compound and is resistant to many high temperature chemicals. It is suitable for vacuum applications and resistant to oils, grease and fuels.Contains 10 pieces tameson.co.uk

Thread on it here with some useful info: https://rennlist.com/forums/996-forum/1468750-repairing-oil-leak-behind-oil-pump-housing.html

Quotes source post: 2831052

Some very useful info here, thanks guys. What size do you reckon I should got up to? Thinking 29 x 2.7mm?

Quotes source post: 2831060

Yeah, i'd even try 29.1x 2.8 2.9 they are cheap so get a few sizes and see what they feel like when offered up.

When you push it in there should be some resistance at first then it'll go. Just smear some oil on the new rings and in the socket. I'll have a look and see if I can find the ones I used. Edit...Unusually I bought the Elring ones from D911 when I bought all the other gaskets and things for the oil pump housing. Elring stuff is usually spot on and OEM (I think)

Incidentally, why has yours got 3 O rings? Fairly sure it should only have 2 in the grooves, what's that other one doing ?

That would be very helpful @Uncle Monty , thanks. @Hooner do Selo definitely do custom sizes? I've looked them up and I don't see anything on their website about it. It would be very helpful though, this has also got me thinking about doing the same on my scavenge pump leak.

Quotes source post: 2831073

The 3rd one is one of the old ones, I noticed that the oil pump doesn't quite sit flush with the face of the block so I thought that maybe putting the third one there might help it seal further. This of course did absolutely nothing as it just got crushed and squeezed outwards as I tightened down the pump. Thought it was worth a try

Quotes source post: 2831074

Yep

Quotes source post: 2831076

Ideal. Have you had custom o rings from them previously?

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And I think you have to fit the cover before you tighten it on as if Don't do that just get 2 new Elring ones and it should be fine but you have to fit the pump cover first I think as some of the bolts go right through so you have to tighten in a sequence as well as the big 4 studs.

The top right rectangular oil port looks like it's scratched, I'm sure it's not but best confirm.

Remember to fit the hex drive pin

Quotes source posts: 2831080, 2831083

I'm a bit confused, you're saying that the oil pump cover needs to be bolted on before I fit the pump to the engine? I can't see how that would make a difference to the O rings on the snout? I'll check again but I'm pretty sure it's just machining marks similar to how the mating surface for the heads would be.

I was going to ask the same about the 3rd o-ring. Hopefully that wasn't causing the problem.

Quotes source post: 2831086

Sorry for confusion I think I was waiting for a new cover gasket so couldn’t tighten up the big nuts as the engine support bracket goes on over it so you have to do it all at once. New gaskets , new O rings , all clean surfaces it should be fine

So where are the ones that are leaking now from? maybe they are just incorrect size and it's as simple as that. I suggested oversize ones thinking you have fitted elring and that they are leaking, if not try some elring ones first.

Quotes source posts: 2831088, 2831091, 2831092

They are Elring, from Design911. Ah gotcha, yes I think I just gave the pump a few light taps with a rubber mallet to help it push all the way on before fitting the engine support bracket. Can't see how it would have, all it could do is stop the pump fully seating against the engine but the two sealing rings sit in past the outer edge by around 5mm so even that shouldn't have stopped them from sealing, and the extra O ring would have been crushed when I tightened the engine support bracket anyway. Regardless, I won't leave the 3rd one on next time round.

Quotes source post: 2831091

You would think new seals and gaskets should sort it, but that's what I did last time I tried to fix this. Hence this thread to try and figure out where I went wrong. All very helpful so far, I'm going to look into ordering some slightly thicker O rings tomorrow, and I have another oil pump on the way in case mine turns out to be cracked.

If you used Elring already then slightly larger ones might do it, but I'd have thought the Elring ones should work fine. Maybe check them with the calipers that they're the sizes stated 29.1 x 2.55mm. Shame we can't all turn up at your place and help get this sorted for you..very frustrating but you're doing everything right. I doubt yours is cracked but..

I'm going to order 2 more of the standard 29.1x2.55 O rings, and also 2x 29x2.8 and 2x 29x3.0. The original size are 34.2mm OD, and the two larger sizes work out at 34.6mm and 35mm respectively. So overall 0.4mm and 0.8mm larger, but that's only 0.2mm and 0.4mm taller than the originals when measured from the surface of the grooves they sit in. I also don't think my oil pump is cracked, but I don't want to risk taking it all apart, find that it is and have no way to move the car back into the garage without putting the cracked one back on. Worst case I have a spare pump to fit, best case I just stick the spare back on eBay.

Wish you luck with it Real pain in the @&£! after all that work..

Getting geared up to have another go at fixing the oil pump leak this weekend. My spare oil pump and oversized O rings arrived today so I test fit one of the O rings on the pump. The new ones are 29 x 3mm where the originals are 29.1 x 2.55mm. They just about fit in the groove on the pump, and they measure 35.6mm outside diameter when fitted where the originals are 34.5mm. What do we think? Too much of a jump in size to fit?

The "0" ring is going to be under compression when is situ, so I think there needs to be some space for the "0" ring to spread. If not there is a chance the "0" ring getting pitched resulting in a leak. Just a thought.

plenty of slippy stuff on the rings and bore when inserting.

It's going to work i reckon

A full 1.1mm more OD than the design... could be difficult to insert but also more difficult to remove if it ever comes to that again, with risk of the snout breaking off in the attempt. Why are there two O rings, was Porsche just making double sure or is there some other functional reason? May have missed this earlier, but there is no damage or scratches in the bore they seat into?

Only One way to find out. This sort of thing is really frustrating when there’s no obvious reason for the failure. Good luck sir !

take a run up with loads of lube and report back................best of luck!

Just on chatgpt:

Thought I'd try and be a bit more scientific about this and take some measurements of the oil pump and O rings. Obviously I can't measure the bore that the pump fits in until I get the original pump off the car again, but given that it seemed to be a pretty tight fit last time I've estimated that it's around 34.6mm, 0.6mm larger than the snout of the pump. I also measured the actual O rings that I have received rather than relying on stated measurements on the parts listings. Then with all those measurements gathered I used an O ring calculator to compare the figures from both sizes of O rings. The recommended values are taken from the same website, and each of the values in my table are an average of the Min and Max values calculated. With my estimated value for the bore diameter, it looks like the oversized O ring might just about work, but if the bore diameter in the engine cases is any smaller than my estimate (34.6mm), then I think it would push the oversized O ring too far outside the recommended figures. Either way, I'm going to get started on the car tomorrow and I will attempt to do what most of you have suggested and use plenty of oil to get the O rings to fit.

Chap on FB had another head with a crack in it that I could've used for the silencer hangers and it's identical to yours

Yours

Lee @ Hartech says they always go in the same place.

Yes that's what I found out too when I was originally looking to get mine welded.

Goodness that’s a rabbit hole Nathan ! Good luck tomorrow

No good news to share unfortunately. Spent all day today pulling the oil pump off again, inspected the pump, all mating faces and other areas that aren't accessible with the pump on. Couldn't see anything that was clearly causing a leak. Tried a test fit of the new (used) pump with the thicker O rings, which didn't work. It sheared the O ring in half as I tried to push the pump into place. So I fitted two new original size O rings, and used sealant as well as the gaskets on the two oil galleries on the pump. When fitting the pump I loosened the two case half bolts either side of the hole to allow the O rings to hopefully slide in easier. Then tightened the bolts again after the pump was in position. Replaced the oil pump cover seal. I also backed out the two bolts that hold the timing chain guides in place to add some sealant on their O rings in case they were somehow the leak. Put it all back together, checked the timing hasn't changed, filled in with oil and coolant, went for a test drive. 30 miles later, had a look underneath. Still leaking. Same spot. I give up.

How frustrating, I feel for you. The infuriating thing is, as is often the case, when it is solved, it is likely to be so obvious.

Not coming through the bolt holes is it? They should be sealed with loctite 242 or 243.

Didn't seem to be but I also didn't really see anywhere that it was coming from. However the bolts aren't sealed with anything as I wasn't aware they needed to be given that the bead of sealant around the case halves join is between the bolts and the inside of the case. It should be possible to remove most of the case half bolts without much disassembly so I can try removing them and adding sealant as it seems the only other option for the leak at this point is the case half join itself.

I've had a good look around the engine again yesterday after driving the car for half an hour, to try and get a better idea of where the leak is coming from. I checked the case half bolts above and below the oil pump flange, all were dry showing no signs of a leak coming from them. I pulled the crank pulley off again to have another look at the front main seal, and while it does appear to be weeping slightly as I did end up with a smear of oil on my finger after touching the seal, the area below the seal is dry so it isn't leaking from there and running down to the pump. When lying under the car and looking up at the front of the engine (back of the car) where the oil pump joins the case halves, there is about 1mm of the oil pump flange that doesn't sit inside the case. This is where I can just about see oil gathering, where it presumably builds up and then runs down along the case half join and then spreads out across the bottom of the engine. Oil gathering on the bottom of the engine. Looking up from the bottom of the engine at the oil pump flange. Circled is the base of the oil pump flange where it fits into the case. You can see the 1mm sliver of the flange that sits just outside of the bore in the case. It's difficult to make out in a picture but this is where I'm seeing oil gathering. The front crank seal from above (red). It is slightly moist with oil but the area below it is dry, including the case half join. Below that in blue you can just see the head of the case half bolt that is above the oil pump flange bore. Everything you can see in this picture (apart from the crank seal itself) is completely dry of oil. Above. Sealant on the oil galleries on the new oil pump. New, standard size O rings fitted. Below. Nice clean mating surfaces on the new pump. Brand new gasket in the background. For anyone who is unsure, blue is coolant galleries, red is oil galleries, and yellow is the bit that pushes inside the case. And these are the corresponding areas on the engine itself. In this picture I haven't cleaned anything so the sealant I tried last time is still left behind on the surface around the oil pump bore. The dampness on the case to the right is from power steering fluid that leaked down from above when I removed the reservoir to remove the AC compressor to remove the chain tensioner to remove the oil pump... You can also see in this picture the sealant squeezed out of the case join below the yellow area. You can't see it squeezed out above or below this but to me this makes sense as those areas are wider where there are bolt holes. Here, the red area is the section of the case half above and below the oil pump bore (yellow in the picture above this). The small green area is the section where you can see sealant squeezed out of the case join in the picture above this. It's much easier to see here why you can see sealant squeeze out in this area but not either side of it, as the bead of sealant is applied to the inner side of the bolt holes. And lastly, in this picture you can see the case halves just after I joined them, and circled in yellow you can see sealant squeezed out in the bores for the oil pump flange and front crank seal. I trimmed this excess sealant with an exacto knife before fitting the seal and oil pump. So all of that would suggest that the oil pump should not be leaking. However, it has now had 3 lots of new seals and gaskets, and on this latest attempt to fix it I fitted a different pump to the original. Each time the leak has remained the same, so in my view at this point I have to rule out the pump and the seals and gaskets on the pump as the sources of the leak. The case half bolts around the area of the leak have remained dry, and as far as I can see I have applied enough sealant on the case half join to prevent a leak. There is no sign of a leak above the pump, and it seems incredibly unlikely given how sheltered this area of the engine is, that oil could be leaking from lower down and being blown upwards to where I am seeing it gather. I am completely at a loss at this point. The only other things I can think to do are to try a set of Genuine Porsche O rings next time round, although I cannot see how they could be different enough to the Elring ones to make a difference to this leak. The other thing that I can do is to crack test the pump that I took off this weekend, to see if there is a possibility that I am installing the pumps wrong and cracking the flange on assembly?

Deleted. By 'pump' do you mean the big console casting with the boss/spigot going into the cases, or the funny shaped pump cover itself?

I haven't but that is something I'm planning to do in order to rule that issue out. However I've now fitted two different pumps to this engine and had the same issue both times so a crack in the pump causing the leak is unfortunately unlikely.

I have noticed that i cannot see the oil pump gasket ? have you not been fitting one? if not the pump may not be sitting correctly. If you have this is very annoying to say the least, as a last resort i would try some bonding sealant some thing like OB1 clean and dry the area and o rings with de greaser and smear it with the sealant, fit the pump and let it dry overnight and just see if it stops the leak. It's worth a shot.

Incredibly frustrating, Someone somewhere will of seen this before. Is the oil pressure ok? The pressure relief valve working properly? excessive oil pressure causing it to leak? Will it leak at idle without driving so you could run it and watch it ? Wondering if there’s anyway to pressure test the system like you would coolant? I’ve never done it ?

Quotes source posts: 2832417, 2832423

Annoying is an understatement at this point. I'm hesitant to try sealant again as I put plenty of sealant on the oil pump flange in my last attempt and that didn't seem to do anything. It's seeming like the case halves are the issue rather than the pump seals, but if that is the case then the leak is very close to where the oil pump flange fits into the cases, because I can see oil gathering on the oil pump flange itself. And I can't see how the oil would get blown back upwards because this area is quite sheltered from airflow. But then I know that there was enough sealant in that area because I had to cut away extra sealant after I joined the case halves. So I just don't get it. I hope so, I've sent an email to Hartech and I'm going to call them tomorrow. Oil pressure seems ideal, drops to 1.5ish bar when warm and idling. Brand new relief spring and piston fitted. It doesn't seem to leak until it's warmed up fully, but yes I could try getting it warm then coming home and jacking it up to have a look while it's still running. That's probably a decent idea. I have also seen it recommended to get some UV dye for the oil to help see the leak easier, so I might do that too. I have been wondering if there could be a too much crankcase pressure or something, but no idea how I'd work that out. One thing I haven't really thought about until now is that the IMS shaft is submerged in oil (I think anyway?) so the oil pump seals do actually have to hold back liquid oil, not just oil vapour under crankcase pressure like I assume the higher up front crank seal does.

Just had a quick Google about crankcase pressure, apparently a healthy engine would have a slight vacuum in the crankcase? A few different sources say this so I suppose it could be true. But then the oil that's in the crankcase is under pressure? I have to admit I don't quite get how the oil pressure is measured. I assume the oil that is being forced through oil galleries is under the 1-2 bar at idle, but I assume it isn't that all of the oil that is sloshing around in the sump is under that same amount of pressure?

IMS shaft sits just about at the top of the oil level not fully submerged but both seals crank and oil pump will be spayed with oil when the engine is running, Oil pressure is created by oil forced through the main bearings and through the oil galleries i can't see it being a problem really.

You can measure crankcase vacuum quite easily with a manometer, cheap to do. Oil isn’t all at that pressure only that in the galleries. Engines generally have crankcase vacuum. Several reasons, If there’s positive pressure the pistons would have to push against it robbing power and potentially pushing oil past the rings into the combustion chamber. Theres always an element of blow by gas past rings into the sump, this pressure would build up and look for the weak points then you get seals leaking. It’s why the AOS is such an important part of the breather system.

I'm guessing you didn't take a pic just after you'd applied the sealant to the case half?

Maybe somethings not right and it’s a build up of crank case pressure causing the leak ? Horrible to have problems after so much work. Been there quite a few times, it’s character building!

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Correct. Kicking myself now for not getting a picture but pretty sure at the time I was panicking about getting the other case half bolted down before the sealant went off

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I was thinking that but from what I've found online if it had excess pressure it would affect how the engine runs and it runs absolutely fine.

It would yes. It’s most likely o ring / gasket / sealing faces somewhere. Hopefully Hartech might help with info? I’m sure they’ve seen leaks in all the years they’ve been doing them Did you say you put it in the engine gurus Facebook page ?

That's what I'm hoping, just as long as the sealing faces in question aren't the case half sealing faces. Yes I emailed Hartech this afternoon explaining everything and they emailed back saying to call them tomorrow and they could put me through to one of their engine builders to discuss the issue. So hopefully they'll have some suggestions. And yes I put a post on the group on Facebook, didn't really get anything particularly helpful from it.

Quotes source posts: 2832371, 2832417

Oil pump meaning the entire front console with the boss that fits into the engine block. What do you mean by oil pump gasket. There is the squiggly shaped rubber seal that goes in between the oil pump console and the oil pump cover, and the two o rings on the flange that fits inside the engine.

Quotes source post: 2832500

i mean on the galleries like what it shares with the water pump on the original fitment, they all should have gaskets, i see you put sealant on the oil ones did you not fit a gasket as well?

This, you cut the water pump part off if you don't need it. This is the top one that cover coolant and oil Have you not fitted these?

Yes I've replaced those with new ones each time the pump has been off. I used sealant on the oil galleries just as extra insurance to make sure that the leak wasn't coming from them

I thought you must have. You would’ve had oil and coolant dripping out everywhere

As I keep thinking about this oil leak, it occurred to me that although I said that I had to rule out the seals on the pump itself as the issue, (given that 3 attempts at fixing the leak with new seals didn't work), that each of those 3 attempts involved identical parts and steps taken. Now, I believe there is a quote defining insanity as "doing the same thing over and over again and expecting different results". Which is essentially what I've been doing... So it's pretty clear at this point that trying again with another lot of standard seals and gaskets isn't going to work. I find myself looking at two main options; The leak is coming from the oil pump flange / bore in the case. The leak is coming from the case half join somewhere above or slightly below the oil pump flange. I suppose my first step should be to determine which of these options it is, and I think the best way to do this is going to be to put some UV dye in the oil, take the car for a drive and get it nice and warm, get home and get underneath the engine, clean off all the oil leaked during the drive, and then leave it running, lay under the car with a UV torch watching the oil pump area for the first sign of some oil appearing. Hopefully if I do this then I should be able to see whether the oil is coming out around the flange on the oil pump and gathering on the bottom of it, or if it is coming out of the case half join and running down and gathering on the pump flange. Because it's relatively easy to do as I have the original pump off the car now, I'll also crack test the flange to see if there's any possibility that I've been installing the pumps wrong and cracking the flange. Assuming that I find the source of the leak to be the oil pump flange / bore (as I've been assuming so far), I clearly need to try something new to get it to seal. As I mentioned a few posts back, I tried some oversized O rings on my last attempt, going from 29.1 x 2.55 (standard size) to 29 x 3, which turned out to be way too big and sheared in half when I tried to fit the oil pump to the engine. So I've been researching some more, and I've found some 29.6 x 2.6 Viton O rings available in 75 and 90 Shore Hardness. I'm thinking that a slightly larger but softer O ring might conform to any roughness or seams in the bore and potentially seal it better. I've found online that it's possible for the two halves of the bore that the pump fits into to be very slightly misaligned, therefore not exactly circular. As well as that, there is also the fact that there is a seam running through the centre of the bore which could possibly be creating a small channel for oil to escape past the O ring if the O ring isn't squeezing into the seam. Exaggerated diagram below. Another thing I've thought of, again if the oil pump seals are the issue, is that there is a small gap between the base of the oil pump flange and the engine case when the pump is installed. This is where I have been able to see oil gathering when it leaks, but I've been thinking that maybe a correctly sized aluminium washer around the base of the oil pump flange could be compressed enough when the pump is fully tightened down to seal against oil leaking out. The green area in the diagram below is currently filled with fresh air when the pump is fitted and I know from my first attempt at this that an O ring in this area doesn't work as it just gets squeezed out of the way. The only issue I can see with this idea is that this gap is left so that the other gaskets on the oil pump console have room to compress properly, and so working out the correct thickness for a washer here could be tricky as it would need to still allow the other gaskets to compress, but also still be compressed itself. As I said already, these ideas all assume that the sealing of the pump itself is the issue, when it is in theory possible for the leak to be coming from the join in the case halves. For now I am choosing to not think about that issue as I have no idea how I'd sort it out if that was the case.

This wouldn’t be a permanent fix but if you apply a really good amount of sealant across the exterior area of the case halves where you suspect oil could come from it maybe be enough to hold it back or at least change the leak characteristics enough to help in diagnosis.

JB Weld has crossed my mind a few times.....

My replies are only really for moral support, I’m sure you’ve thought of all these things.

All replies and suggestions are very much appreciated.

Have your scavenge pumps stopping leaking now?

One of them is still leaking because I haven't got around to changing the O ring on it yet.

Loctite MR5923 is good stuff

Re scavenge pumps: The 4 inner screws each have a tiny o-ring that sit inside a washer which in turn sits underneath the bolt head. Once these screws are cracked open those o-rings need replacing or if reusing the old ones, sealant must be applied in addition to them. They are distorted after all these years, so hard to measure to get replacement, which porsche don't list as a spare part. The four outer screws go into blind holes so no sealant required for those. If a new O-ring doesn't seal, then the bore surface is too uneven/pitted due to corrosion. I wouldn't put any sealant on the o-ring but instead in the 'throat'/corner between flange and pump body itself, basically the spot where you had the 3rd o-ring on the oil pump console. O-ring lubricant with swelling agent I would however put on the o-ring (molykote 55).

Quotes source post: 2832775

Yes I found out about the tiny O ring on the inner bolts as that's where one of my leaks was coming from. Used a bit of sealant on the bolt as you said. However I know for certain that at least 2 of the 4 outer bolts are not a blind hole, they go in a through hole which reaches inside the head, so I have used sealant on the threads of the outer bolts too. The remaining scavenge pump leak is (I think) due to surface corrosion on the mating surfaces, so I've ordered a thicker O ring than the factory size to hopefully seal that properly. There is definitely no corrosion or pitting on the oil pump bore, but as I mentioned I think the two halves of the bore could be slightly misaligned or the seam between the halves is allowing a tiny gap. Thanks for the tip on the lubricant, I'll look into it. I don't think sealant at the base of the oil pump flange would work as the gap is too big, I'm going to try and measure it but at a guess I'd say it could be around 1mm.

I mean the only way for the two halves to not be perfectly aligned would be if the dowels weren't present or that the two halves were not a pair from the factory, like from a previous engine rebuild using half a casing from a different engine. Having said that it makes no sense because it didn't leak before..did it?

I think it's unlikely too but I think that if one of the dowels ended up slightly out of shape from being removed with a mole grips or something then that could do it. I do remember filing off a small burr on one before refitting them. I had left the dowels in the cases when I dropped them to Hartech and when I got them back the dowels had been removed and I got them back in a plastic bag. To be honest I can't say whether it leaked before the rebuild or not, I didn't really look around it too much before taking it apart.

It certainly didn't look too great..

Just been on the phone with Lee from Hartech for some advice on this issue. He said it's an issue he's had a couple of times before, and the number 1 piece of advice he has is to make sure the bore is nice and clean, no burrs or sharp edges, use a bit of grease, and make sure the pump slides in perfectly straight, no wiggling or side to side movement. He did also advise me to check the pump carefully for any hairline cracks because he's also seen that before. They also apparently only use Genuine seals for the pump, and sometimes they do have to use a bit of sealant around the outside of the O rings to make them seal. I mentioned my idea to use slightly thicker O rings, and he said that is something that they have looked into as well, and would be a good idea if Genuine Seals and some sealant doesn't work. Nice to get some advice direct from the experts.

Quotes source post: 2832956

I bet its a relief to know its not something obvious you overlooked and that they experience stubborn oil leaks at times too..................

Lee's bob on and knows his onions.

It is, although the fact that I have already tried nearly everything he suggested still makes me wonder if there's something I'm missing

When Lee say's "we sometimes have to use sealant..." does that mean that sometimes a rebuilt engine will start to leak and they then have to remove the pump again and add sealant, I mean you couldn't possibly know it would leak until you run the engine up could you?

Quotes source post: 2832973

I got the impression that yes, as you say, they have had engines put together as mine was, found it leaked and the solution was to use sealant. He certainly wasn't suggesting it happens often but it seemed like they've had to deal with this issue multiple times before.

Quotes source post: 2832844

You're right. I checked pictures of mine and found that the 2 in the head are thru-holes. The pump body is a snug fit inside the bore. I think you'll find that sealant in the throat doesn't need to bridge a gap and will seal well.

Ah sorry, you meant the scavenge pump on the head when you mentioned using sealant? I thought you were referring to the main oil pump.

Got a bit of an update on the oil leak situation. As I think I mentioned previously, before I go taking the oil pump off yet again, I want to do some investigating to make sure that I'm not completely wrong about where the leak is coming from. So this morning I took the car out for an hours drive to get it all nice and warm, then came home and got the rear of the car up on jack stands. I had a look underneath, saw that the oil leak was definitely still there, cleaned it off with brake cleaner and started the car up again. I then proceeded to lay under the car with a torch looking up at the oil pump area, waiting to see signs of a leak. I think I must have been lying there for about 15 minutes before I saw anything. And not where I expected it. Well done to @Alex for pointing it out several pages back, but it appears that part of the leak is coming through the case half joins specifically around two of the lower case half bolts. I cleaned these off several times during the 45 minutes or so the car was running for, and they consistently came back after about 5 minutes. So these are definitely contributing to the amount of oil I'm seeing gathering on the bottom of the engine. Now by the time I saw these leaks appear, I still hadn't seen any sign of a leak from the oil pump. I think I watched it for another 10 minutes or so, still saw nothing, and decided to get out from under the car to rev it a bit in case the leak only leaked under load. And when I got back under the car, this is what I saw. The picture is crap I know, but it's the best I managed. The blue area is what you can see of the oil pump flange from under the back of the car, and in the middle of it in red is a dark spot which is a drop of oil. It wasn't very much but enough to be clearly seen as a blob of oil, however not enough that it could have run down from above and gathered where I was seeing it. And since I hadn't actually seen it appear from anywhere, as it had just appeared while I wasn't under the car, I cleaned it off with brake cleaner and went back to watching it to see if I could actually spot exactly where it was coming from. And I'd say I waited half an hour under the car watching the oil pump the whole time, and the oil never reappeared. So quite a confusing couple of hours, but having thought about it for the rest of today, I think it might be possible that the majority of the oil I've been seeing gathered under the engine is actually from the two leaks at the case half bolts seam. The oil pump is clearly leaking slightly as I definitely still see oil higher up than the two bolts after a drive, but it's potentially a much smaller leak than I thought previously. The other possibility with this discovery is that the front main seal is the source of this leak from higher up, as the amount of oil is much less than I've been expecting when I've checked the seal before. This does contradict what I said about the amount of oil I saw being too little to have run down from above, but I have been wrong before. Back to the issue of the two case half leaks. As said a couple of pages back, I didn't use any sealant on the case half bolts as I simply wasn't aware it was necessary. I still don't understand why it's needed, but clearly it is. So as an attempt to sort out these leaks, I removed the two case half bolts one at a time, covered the threads in sealant and reinstalled. It was somewhat encouraging to find that the threads on both bolts were wet with oil when I removed them, so hopefully the new sealant may sort out the two lower leaks. I'm going to allow the sealant to cure fully before I drive the car again, but it should be interesting to see if / how it changes the amount and position of the oil leaks. I'm hoping to see that amount of oil is reduced, but probably will still be able to see oil on the bottom of the oil pump flange. If this happens then I think I'll just replace the front main seal and see if that changes anything before I have another go at sealing the oil pump. I did also crack test the original oil pump this morning, and as expected it's completely fine. So it rules out a cracked oil pump at least.

Well it sounds positive, insofar you have narrowed the leak down. I hope the sealant cures and does the job. Fingers crossed for you .

Just looking at the 2nd photo of the case bolts and I’m sure it’s not but it looks like a tiny crack to the right of the wet patch.

Here

I can see what you mean, I'll have to have another look but from another picture of the same area I'm pretty sure it's not a crack. I also spent quite a bit of time staring at that area today so I feel like I'd have spotted that.

Kudos for spending that much time lying under a hot running engine! It leaked after revving the engine, so after oil pressure was raised. The highest pressure would be at the oil pump, so right at those O rings. Someone posted a ChatGPT response a few pages ago about there being 2 o rings to seal against the oil pressure from the pump. I reckon that's still the source. Crankshaft seal would leak whenever the engine is running.

Once again, I spent my weekend removing the oil pump in another attempt to fix the leak I've been finding. I've done this enough times now that it only takes me about 3 hours to get the pump off, and another 5ish to clean everything up and put it back together. I started by taking the car for a drive for 40 minutes or so to get everything warmed up and get some fresh oil leaking out. I then got into stripping it down straight away before the oil drained away as I wanted to give myself a good chance to see where it was coming from. This is what I saw immediately after removing the pump. I made sure to check around the pump beforehand, and as it has been every time, there is absolutely no sign of any oil above the oil pump, only below. Obviously you can't see it here, but I was watching this area as I pulled the pump off, as I knew that oil would dribble out of the bore once the pump was fully removed and I wanted to see were the oil had been leaking before this happened. As already mentioned, and as I was expecting, there was no oil above the oil pump bore, and it was wet with oil below and right up to the bottom of the bore. I can't see how oil could leak further down and travel up, so it must still be leaking from the bore itself. Next I cleaned up all the mating surfaces, and roughed the surfaces along the case half join with a wire brush and sandpaper before cleaning it again. I also removed the case half bolts above and below the oil pump bore and covered them in sealant before refitting. So I now have all 4 case half bolts near the oil pump covered in sealant in case the leak is coming from the case half join around the bolts like I had found on one of the lower bolts. This will be controversial, but I wanted to do what I could to make sure the leak isn't from the case half join itself. So after cleaning and preparing the surface thoroughly, I used some High Temp JB Weld to cover the case join seam above and below the oil pump bore. Obviously this is not ideal, but if the leak is from the case join then the engine needs to come apart again anyway. Here you can see the difference between the original size (left) and new oversize (right) O rings. The original size is 29.1 x 2.55, the new ones are 29 x 2.65. Previously I tried 29 x 3 which was way too big, so I was hoping that these slightly oversized O rings would still fit but just give a bit of a tighter seal. I also cleaned the pump flange, checked for any cracks and removed any burrs. And did the same for the bore in the case. After I let the JB weld on the case dry for a bit, I applied a layer of sealant to fully cover both O rings on the flange, and also smeared sealant across the case seams inside the bore. I then put the new gaskets for the coolant and oil galleries in place and had a go at fitting the pump. At first I thought the new O rings were catching in the bore, but when I got underneath and had a look all seemed fine. I was able to get it in just past the first O ring before I think the combination of the bigger O ring and the amount of sealant made it very difficult to push it in any further. I stopped for a minute or so while I checked that the pump was definitely going in straight and the end of the IMS wasn't out of position before I decided to use the nuts on the 4 engine mounting studs to slowly push it into place. Of course the number 1 thing not to do with these pumps is to try and push it in crooked, so I was very careful to only turn each nut by a quarter turn before moving to the next one. By doing this I eventually got the pump fully seated, and then started to put it all back together. With the car all back together and back on the ground, I left it overnight to allow the sealant and JB Weld to cure properly before starting the car up. I took it for a careful 20 minute drive, and once again, there is still a leak. Almost exactly the same amount, pattern and area as every other time. And yet again I found myself with a roasting hot exhaust inches from my face, lying under the car looking up and watching for a leak. In this picture you can see that the gap between the base of the oil pump flange and the surface of the engine case is now entirely filled with sealant. And yet, in the red circled area, I could see oil start to appear and eventually dribble down the case join to where I'm seeing it gather and drip off. I am well and truly lost at this point. With the new O rings and the amount of sealant I used I am not sure how it is physically possible for oil to escape. It is definitely still coming from the oil pump bore, so apart from my idea for a washer in the gap (which is currently full of sealant) I'm not sure what else to do.

How good do each halves line up with each other on the bore here and at the lower joint on the diameter? Can you run your finger nail over it and it feel exactly in line or can you feel a step?

Tried exactly that when I had it apart, can hardly feel the seam at the top, can feel the one at the bottom but it's very smooth, didn't feel out of line.

the slightest of steps can create a leak.

Yes, but I'm fairly sure there isn't much of a step at all, and if there is a step it has to be small enough that the sealant would take care of the gap. Nothing is really making sense with this leak. Apart from taking the engine out again the only thing I can think to try is a perfectly sized aluminium washer in the gap (green).

is there an option to swap out the o-rings for a different seal? to allow greater contact area

Quotes source post: 2835433

Not really, the pump is already quite a tight fit so I think the O rings get squashed which increases the contact area.

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Copper might be better: softer, shouldn't chemically bond, and historically used as a seal on sump plugs. This is incredibly frustrating and I really feel for you Nathan.

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I keep finding contradictory information on whether copper or aluminium is better for a crush washer. It seems to me that aluminium is a little easier to crush than copper for what I'm thinking of doing. @Alex you don't happen to have experience of making custom sized washers do you?

I can't imagine how you're managing to stay sane over this. I'm not sure a crush washer will work as you're not getting much force onto it and it's not in the right place, a sump plug has more force and it's directly around the washer with the sump plug having a flange for it to sit on, you may end up doing more damage, I don't know but that's what I'd be worried about. Something about this just doesn't make sense, I think if it was seeping past the 2 O rings somehow, we'd see far more cases of this happening in the Porsche M96 world, I did this exact job recently and no issues at all. That housing has so many options to leak coolant and oil and each time you have refitted it, it always leaks oil at the exact same point. Coolant would be more likely but this hasn't happened, it's always oil at that place. Very strange indeed. I wonder if there's a tiny crack/fissure.

Quotes source post: 2835479

I can make a plain custom size washer but I can't make a crush washer, which is what you'd need to seal it. Can you not source a crush washer the right diameter? https://www.ebay.co.uk/itm/388516004413?mkcid=1&mkrid=710-53481-19255-0&siteid=0&campid=&customid=&toolid=10001&mkevt=1

I’d maybe try something like these you can get them bespoke sizes if needed, and I think they will be easier to squeeze without causing any damage

Quotes source post: 2835520

They look like they might do the job. Cork swells and will go brittle over time (but so does rubber), but it probably doesn't require the force (as Uncle Monty rightly pointed out) a crush washer would need to work. Arguably even just a plan rubber washer might work.

Agree, a plain rubber washer would be a good idea but you'd need to get the thickness just right. I can't remember if you've already used RTV as a full ring around the flange but that would ensure a perfect seal as long as it super clean before. There's not much of a flange though.

Quotes source posts: 2835503, 2835514, 2835520, 2835531

I'm not really sure how either to be honest! Yes I agree with you on the crush washer, as you point out there's nothing to apply force directly around the washer like there would be on a sump plug. I guess what I really mean is that I think a washer that would exactly fill the gap could work. Where I could apply sealant to both sides of the washer so that it would essentially be the same as how the case halves are sealed, a solid surface meeting another solid surface with sealant in between. Clearly I'm not going to be able to seal the oil pump bore itself to stop oil getting out, but if I can use this washer idea to contain it from going any further I'd be happy. I've been looking but no I can't find anything off the shelf. The measurements I need are around 34.2mm ID, 38mm OD and (I'm guessing) 1mm thick. As I've said above, I'm now thinking that a crush washer isn't the way to go, but a solid washer that exactly fills the gap might work. I'll need to figure out a way of measuring the thickness I need, as part of the problem is that the reason the gap is there is to allow the two metal gaskets to squash slightly and seal, and a washer that is too thick would stop that from happening. I haven't seen those before, I might look into them. Would the cork not absorb the oil and eventually weep anyway? A plain rubber washer is also something I hadn't thought of, I'll look into that too. As you say though, there isn't much of a flange so I'd be worried that a rubber washer would squeeze out like when I tried a third O ring in the same position. I kind of mentioned it earlier, but yes with the amount of sealant I put on the O rings, enough has squeezed out of the bore that there is basically a solid ring of sealant around the base of the flange, where we're talking about putting a washer. And the oil is still getting through that. Obviously excess sealant squeeze out isn't anywhere near as solid or consistent as an O ring or washer would be so I still think it's worth trying. I do also have a 3D printer so I'm thinking if I find a material with decent temperature resistance to print a washer from, it would be harder than rubber but softer than aluminium so it might make a good seal? As always, I really appreciate everyone's input on this issue.

How on earth is it getting past 2 O rings though? There's a lot of fittings like this on these engines, even on the Turbo the 2" coolant hoses that plug into the engine are a simple push fit with a single O ring and they don't leak.

I think there's a red herring in here.

I think I'd be inclined to cover everything in something that highlights where the oil is coming from. May put masking tape on all metal surfaces and round each part of the diameter of the snout. That would then turn brown where it's leaking through and you can exactly pin point the issue. You're still not 100% sure it's getting past those o-rings and not somewhere else are you?

can I ask is the car leaking if not being driven? If so is it from the exact same place - I am just thinking from an alternate angle, could the oil actually be getting blown up whilst driving so its showing the leak as coming from the pump entry point but in fact could be coming from below and ending at this point..............I know it sounds daft but surely at this point anything is worth consideration..............

Exact spot everytime Moo and it's dribbling down, Nathan is watching it form below the snout and eventually drip out albeit not much. He's under the car at idle so not moving

Quotes source post: 2835582

is there any way to check if the spout is out of line in any way? I have read they can break off if manhandled but suppose they could also be bent slightly too?????

Deffo needs some way of visually tracing where it's coming from.

Quotes source posts: 2835574, 2835576, 2835577, 2835579

2 oversized O rings + sealant at that. And no I have no idea either. You would think so but there simply isn't anywhere else in the vicinity of where I'm seeing the oil that it could be coming from. I think I mentioned this before but no, it doesn't leak unless the engine is running and warm. On Sunday I was able to lay under the car and watch the oil slowly weep out from the bottom of the oil pump flange, highlighted in purple below. It was not a windy day so no chance of it being blown upwards. I also cannot understand how it could be getting past the O rings, at this point I'm assuming that it's getting through the case half join just below the bore. That also doesn't make sense to me, because it implies that there isn't enough sealant in the join in that area, when I have pictures and can remember having to trim away excess sealant in the bore.

Quotes source post: 2835584

Casting usually snap before bending.

Quotes source posts: 2835582, 2835584, 2835585, 2835587

Thanks Monty, yes exactly I've been watching it (laying under a running engine for half an hour just to see a tiny drop of oil appear is not fun) It physically will not fit if it was bent or out of shape in any way. As Alex says, this particular part is known for snapping if installed incorrectly. I've driven the car for about 3 hours since this weekend and everything is absolutely fine so I feel confident in ruling out any damage to the pump. I've thought about adding UV dye to the oil but from what I've read it wouldn't help a whole lot for what I'm doing.

If you apply masking tape around the diameter of the snout between the o-rings and on the outside of the o-rings, you should see exactly where the oil is getting through. You have 4 places it's getting through - outside and inside diameter of both o-rings.

I get what you mean but I don't think there's even enough clearance between the snout and the bore for a layer of masking tape.

These grooves need to be super clean (photo below) and the bore needs to be super clean where the o-rings sit. My money is on the very slightest step between to 2 halves of the bore where the o-rings are when assembled.

Quotes source post: 2835592

Colour it in with something that will wash off with the oil like a dry wipe marker.

Quotes source post: 2835593

Yep, everything got cleaned with fine Scotchbrite and brake cleaner before installation. Your suggestion that there's a small step in the join between the case halves makes sense, but then I'd expect that the combo of thicker O rings and extra sealant would take care of that. And if it hasn't, what else can I possibly do at this point? If it is the case that the two halves of the bore don't quite match, then that would have to be something caused by the initial machining of the case when it was first made, and you would then assume that this leak would have occurred before in this car's life. I'm thinking about a custom washer to fill the gap to basically ignore the issue of the oil somehow getting past the O rings, as it seems no matter what I do that will still happen, and to provide an external seal between the pump and the case to prevent the oil from going any further.

I'm a bit late to this party but leaking past two properly fitted O-rings is a pretty unlikely situation. I suspect the seam in the case halves is causing the leak, it's not very good practice to have a seam on an O-ring seal but I guess it worked at the time. Note that oversize o-rings don't necessarily make it seal better it could be sealing worse. I would be tempted to use a crush washer but as an initial trial why not just use RTV? a bead around the base of the feature would at least allow you to confirm that the leak is located there even if it doesn't seem a very permanent fix. Apologies if this has been discussed. As far as crush washers go I would go for copper, you can anneal copper very easily using a blowtorch and that makes it extremely pliable, not like aluminium crush washers. EDIT: a bit out there but could you press a thin wall sleeve into the hole? Would probably require the oil pump snout to be machined down for clearance though.

rather than a crush washer to create a seal why not try something like a then layer of leather, it would compress a little but would create enough of a seal to see if that cures the problem or if it is somehow weeping out of the case half joint.............plus leather is easier to cut and shape with a scalpel. what about a thermal imaging camera, could that show warm oil weeping? I appreciate everything would be warm but they do show up variations in heat......and may show the case joint as warmer than the surrounding area indicating it could be the culprit

Quotes source posts: 2835599, 2835601

Yes I think we're all thinking the same thing RE the case half seam being the issue. This time round I do essentially have a bead of sealant run around the base of the pump like you say. The issue with it I think is that the gap is reasonably big (1mm or so) so I feel that the sealant would be more likely to squeeze outwards rather than the create a solid seal across the gap. My issue with anything other than something fairly solid like hard rubber or aluminium is that the space for something to fill the gap is going to be around a 2mm wide ring (34mm ID, 38mm OD) and only about 1mm thick. So I can't see a softer material like rubber or leather staying in shape well enough to form a seal, I think it would get squeezed out of position before it compresses to form a seal.

Also I would like to point out that I'm not intending to come across as not wanting everyone's ideas or shooting them down, I just feel that explaining my viewpoint and debating the pros and cons might help come to a solution.

A obvious question but has the bore where the snout of the pump fits been checked for ovality? I'd get good internal micrometre in there just to rule it out.

Quotes source post: 2835605

Not possible, see yellow circle:

Quotes source post: 2835605

That's not something I'd thought of to be honest. The bore in the case doesn't have anything moving in it to cause it to go oval anyway. It is a good point though, although any ovality would have to have been there from when the case was originally machined.

Depends on how much seal is between the 2 halves and how much was between when they first machine the halves in situ.

Quotes source post: 2835610

Ah yes, good point

What diameter is the bore?

Quotes source post: 2835614

I'm not exactly sure, each time I've either not had the tools or have forgotten to measure it. The snout on the pump is 34mm exactly, and there's very little clearance so I'd assume it's around 34.5mm at most.

will be 35mm I bet.

The issue with using a solid crush washer (aluminim, copper) is that you still need compression on the metal gasket so getting the thickness correct is going to be a nightmare too thin and you're not doing anything, too thick then you are holding the pump away from the block in the other sealing faces and your problem is even worse! There are oil compatible sealants out there which will seal larger gaps, the oil isn't under pressure there I believe as it's just the drive for the pump which works in your favour. Loctite SL5900 for example will seal up to 10mm (!), although you need to leave it for 14 days... https://datasheets.tdx.henkel.com/LOCTITE-SI-5900-en_GL.pdf This is the stuff Porsche recommends for the cam covers btw

Quotes source posts: 2835616, 2835617

I'd have guessed that too, but when I was working out sizes for the O rings I found that the outer diameter of the standard size O rings would only be around 35.2mm when fitted to the pump snout, which wouldn't give anywhere near enough compression to form a seal. If the bore is 34.5mm or less then the factory size O rings will compress enough to seal. Yes the thickness of washer needed is the main issue with that idea. I'm thinking of either making some custom feeler gauges to check the gap, or maybe I could ask Hartech if they could measure the gap on one of their engines during the build. If I was to go ahead with the washer idea I'd want to get a few different thicknesses made, in 0.1mm increments or something so I could just test each of them during install to get it right.

Irrespective of the bore size is there a difference in dimensions say horizontally to vertically. Agreed it looks impossible to get a micrometer in there but internal digital callipers might show something? In any event it could just be a tick in the box for no ovality issues.

Quotes source post: 2835622

I will make sure to measure it next time I try to fix this. I'll also ask Hartech, it's possible that they measure these things when doing work on the cases?

I wouldn't be surprised if they have a size sleeve / plug they put in there on assembly to ensure the halves line up perfectly. O-rings can handle a bit of ovality or variation, it's steps they can't handle as the high side holds the o-ring off the low side right on the joint.

Just to explain my idea further, I've drawn the shape of the washer I'm thinking about in orange. The idea being that the thin section is almost exactly the same thickness as the gap, or possibly 0.1mm or so less than the gap. I'd then apply sealant (purple lines) to seal the washer to the pump itself, and also against the surface of the case join. If the oil is getting past the O rings through the case seam, this would cover the seam on the outside and prevent the oil going any further.

could it be possible the case is allowing oil past the back of the O ring via the case halves joint? Where arrow is. Is there a slight gap at all that can be filled with something like a solder, or anything similar then sand the face back to flush? Even a super glue/epoxy to allow it run in and wipe off the surface residue?

Quotes source post: 2835634

That's what I'm assuming, yes. I did wipe sealant across and into the seam before I fitted the oil pump this time.

Something like a heavy duty neoprene might work but getting it shaped like that would be an issue.

Quotes source post: 2835636

but if there is oil in there the sealant wont actually adhere to it - maybe the seal is working in part but still allowing oil to bypass even that - it might need (and please correct me if wrong) some carb cleaner, degreaser and heat to burn off the old oil to produce a clinically clean surface to both sides.............

Quotes source posts: 2835637, 2835639

Maybe, but I did go through about 4 litres of brake cleaner on Saturday when I was cleaning everything before I fitted the pump........ Is this still with a view of using it like a crush washer or as an alternative material for my current idea to just fill the gap without compressing the washer?

I was thinking of a type of crush washer but like you say the flange is so narrow I fear it will be pushed off the lip. If it was shaped like you have done above you'd have a better chance but how would you get that made in the correct material. RTV applied quite liberally onto the flange and then fitted should work.

how about some PTFE tape?

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Everyone has been mentioning RTV, but is this a specific product or just a general term for a liquid sealant that dries to a rubbery material? I've been using this stuff on everything so far.

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I think it'd just get torn or pushed out of the way during installation

Quotes source post: 2835669

RTV stands for Room Temperature Vulcanizing silicone sealant, which cures into a flexible, rubber-like seal when exposed to air. So given the temampture you will likely need a high temp version of which there are many. Some work better is oilly enviroments, others not. Some ideas below. Permatex Ultra Black Maximum Oil Resistance RTV Silicone Gasket Maker or Permatex Ultra Copper RTV Silicone Gasket Maker

Quotes source post: 2835678

Ok so looks like what I have been using is essentially the same thing.

Did some measuring this evening to see if my washer idea would work. I've got a spare oil pump now and I kept the old gaskets from this weekend so I was able to pretty easily measure what the thickness of the washer would need to be. I placed the old gaskets in position on the pump (as they will be closest to the correct thickness when installed on the engine) then used a steel ruler to bridge across between the tops of the two gaskets, and measured down to the surface at the base of the oil pump flange. I also measured down to the surface of the gaskets, then by subtracting these two measurements I got the thickness that the washer needs to be to fill the gap. My measurements are as follows: Top of ruler down to oil pump flange base: 26.7mm Top of ruler down to gasket surface: 25.7mm Therefore, the thickness the washer needs to be is, as I guessed before, 1mm. Taking the rest of the measurements is easy, and after a couple of minutes in CAD, I have this: And another few minutes on the 3D printer, this: I would plan to get at least 3 of these made in aluminium, if not a few more, each with slightly different thicknesses, one at 1mm, another 0.9mm, another 1.1mm, so that I could test fit each of them and decide which one is the best fit. If I have to go slightly undersized to allow the gaskets to compress fully that should be ok as I'd use sealant on all surfaces of the washer which should easily take up any free space. The design of this washer would give me around a 5mm wide ring to seal against the mating face of the case halves, which would ideally cover the first 5mm or so of case join seam below the pump bore and hopefully prevent the oil that is getting past the O rings from going any further.

Is the spare pump knackered? If not would it be worth trying (on the off chance you haven't) to eliminate an issue with "O" ring surfaces. Just a thought. Otherwise looks a good plan.

Quotes source post: 2835801

Nope, this is my original pump, the one currently on the car is a spare I bought off eBay. Neither are cracked, and both leak in the same place so I've ruled out the pump as the problem.

Just saw a video of the oil pump console being removed, looked like quite a struggle just to pull it out and that's just the compression of the O rings resisting the pulling force. So kudos again for doing that so many times. But it made me think its unlikely to leak past those o rings. More likely that it's coming out on the case joint due to gap in the sealant between the mating surfaces of the case halves somewhere in that area. Didn't you pull out a case bolt that had oil on it (or was that elsewhere)? Oil would have gotten to the bolt along the case mating surface through a gap in the sealant.

Wow what a job. This one’s definitely testing you Nathan .. I’m picturing Basil Fawlty, Have you tried thrashing it with a bush?? I’m still digesting everything you’ve done. Really NOT wishing to shoot down your washer idea but I think how many thousand m96 are out there and not leaking in this area it doesn’t make sense to me? Somethings a miss, you shouldn’t need to do that. If it was a common occurrence I’m sure there would be info on the web by now you wouldn’t be the first to find it? There shouldn’t be pressure at any of those joints to cause a leak that some well placed sealant wouldn’t fix to my mind? Adding some loctite 5923 ? .. You’ve tried a second pump highly unlikely 2 pumps are cracked It doesn’t leak if you leave it cold standing. So it’s heat expansion, oils thinner, I keep coming back to case half joint ? (I know you don’t want to hear that) you’ve put JB Weld there should at the very least change the character of the leak ? I’ve had mixed success with JB Weld on bodges over the years it must be said. Hairline crack in the case, expanding when hot ? You’d never see it with your eye. But then you had sealing problems with the scavenge pumps too ? Everything assembled correctly inside, is more pressure coming out of the oil pump snout area than the o rings were designed to seal? Horrible situation.

What oil are you running on? Might sound daft but when I ran on 5w 40 or thinner, my bell housing weeped (from the IMS cover plate). When I changed to 10W 50, it stopped weeping. Are you on a thin running in oil?

Quotes source post: 2835863

Currently on 5w40 fully synthetic, Hartech recommend it for the first 2000 miles or so then to switch to the fancy 10w50 stuff. That is a very good point, I know I've been going on about ways to fix the leak the last few days but after it continued leaking after this weekend's work I've been thinking I might just leave it for a while and see what happens. It's not a major leak and I have managed to fix the other leak from the scavenge pump. If I can deal with it for another 1500 miles and change to the thicker oil then I'll see if that makes a difference.

I also have a slight oil leak in this area but I haven't gotten round to looking at it as I do so few miles and it was at the bottom of a very long list of jobs, which has now become quite short (famous last words!). When I got my car there were obvious signs of damage to my sump plate (bottomed out) so I replaced it and I assumed that this knock was the likely cause of the leak?

I can't get my sump to not leak. I must have replaced it 5 or 6 times using different RTV , letting it partially cure etc etc but it still leaks slightly but no drips.

Quotes source posts: 2835827, 2835853

Thinking about how to fix this the 'proper' way just leads me round in circles at the minute. The leak appears to be coming from the oil pump O rings, so I replace them. No difference. Try again with sealant. No difference. Try again with sealant, oversized O rings and sealant everywhere else that oil could come from. No difference. Get suspicious that it could be the case half join. Fill case half bolt holes with sealant and cover the case half seam with sealant. No difference. Double check everything by watching under the car for a leak. See that the oil is still appearing from the bottom of the oil pump bore. Oil must be getting through the bore somehow. O rings or seals must not be correct. And I'm back to the start. Literally everything I've done has not made a difference to this leak. It appears from the same place, in the same quantity no matter what I change. And yet it is still definitely coming from the oil pump bore, I have watched it happen. As mentioned, if it was actually coming from the case half join somewhere else, either the sealant I applied to the seam would change or stop the leak, and most importantly, I wouldn't be able to see if appearing where it is appearing. The car runs absolutely fine, revs fine, oil pressure is always good, drops to 1.5 bar at idle when warm. No weird noises. I've fixed all the other leaks I initially found. But still this leak is persistent. None of it makes sense. All this leads me to the point I'm at now with this custom washer idea. I have tried all the 'normal / proper' fixes, and none of it has worked. There's not enough evidence of it being the case half join for me to go tearing down the engine again, so I'm willing to try some more unconventional options to try and stop this leak. My washer idea would allow me to have a solid piece of material, with sealant in between, pressed and held against about a 5mm ring (blue in the picture) of the case join around the oil pump bore. This would be held there permanently, and if the oil leak is coming from somewhere on the first 5mm of the case half seam below the pump bore, which is where I've observed it coming from, then it would hopefully provide a seal and stop the oil from leaking any more externally.

You ve got absolutely nothing to loose mate, give the washer a go!

Fingers crossed for you mate. Hope it works.

Just been double checking my measurements and these are the 3 different sizes I think will be best to try. The gap I'm trying to fill is almost exactly 1mm, but whether the other pump that's on the car is any different is the question. If I get these 3 made I should be able to test each of them by bolting the pump on with the old gaskets to check which is best. I'm also not quite sure what thickness I should leave, if any, to allow room for a layer of sealant either side.

In the interest of keeping myself sane, I have decided to ignore the oil leak for this weekend and get on with some of the other things that need doing. I've never owned anything like my 996 before this (my previous fun car was a Mk2 Golf GTI), and in the time I've had it back on the road, I've found myself not quite enjoying driving it as much as I thought I would. I have put this down to the fact that despite it now having essentially a brand new engine, it does still have some issues and things that make it less enjoyable to drive. The persistent oil leak aside, things like the gearshift feeling much stiffer than I think it should, some gearbox noises, creaky suspension, and central locking / alarm system not working right, all add up to spoil the fun a bit. However, I of course still have faith that I can fix these issues to make it the car it should be, so I've made myself a list of things to replace / adjust / improve. The top of that list is new engine mounts and new gearbox oil. Chosen for a few reasons, but mainly because these items have the most potential to fix a number of the issues with the car. Both items should have an effect on the gearbox noise and the gearshift feel. So this morning I got started swapping out my old, leaking engine mounts with some new, 964 RS mounts. I knew I needed to replace them when they started leaking that horrible brown oil on me the last time I took the oil pump off, so I went looking online for a reasonably priced option. I came across a set of nearly new, Genuine 964 RS mounts, for only £120. All the washers and fixings included, all I needed was some 20mm longer bolts to make them work on a 996. It only took about an hour to remove the old and fit the new, including cleaning up the nuts and bolts I was reusing. I went for a drive straight away, and I have to say that it was £140 well spent. The gearchange immediately felt better, though not amazing, and I felt like moving away from a stop was smoother with the engine moving around less. There is definitely a bit more vibration in the cabin when idling, but nothing terrible and it's absolutely fine when moving. The gearbox noise that I've been noticing (a hum / whine when decelerating/off throttle) seemed to be still there, but quieter. Next on the to-do list was a gearbox oil change. Part of the reason I'm not that concerned about the gearbox noise is that I have an invoice from Sports + Classic in 2015 (only 26,000 miles ago) for a full gearbox rebuild including 2nd + 3rd gear, synchros and bearings. But still, there's no invoices in the service history showing a gearbox oil change between then and now, so I decided it was worth doing. I purchased 3 litres of Motul Technosynthese 75w-90 as it has some good reviews on here especially for higher mileage or noisy gearboxes. I got the gearbox fill and drain plugs undone fairly easily, probably thanks to the rebuild, and drained the old oil. I know people mention gearbox oil being smelly, but this stuff was incredibly bad. It also didn't look too good, completely black and slightly shimmery, so I was glad I was going to the effort of changing it. I must have spent about an hour filling it up again because my oil syringe only holds about 300ml, but I got there in the end. While I was under the car I worked out how to adjust the throttle cable as I've noticed that it seems quite loose on the throttle body and the pedal has a bit more travel than I'd like before it does anything. I struggled to find instructions online, and I thought it was counterintuitive, but you basically have to twist the thicker upper part of the cable junction box to the right (tightening) to loosen it, and then pull it apart to increase tension, not pull it together like I first tried. After doing this it improved things nicely, where the cable joins the throttle body is much tighter and the throttle pedal feels much better. With all this done I went for another drive to see had I improved things. The new gearbox oil along with the new engine mounts makes a big difference to how smooth the gearshift feels, although still not as smooth as I feel it should be, I might have a look at readjusting the cables. Interestingly, the gearbox noise didn't seem to change much with the new oil, it might be slightly quieter but that could just be placebo. To me this suggests that the 'gearbox noise' isn't actually the gearbox at all. As mentioned at the start, I'm totally new to 911 / 996 ownership so maybe this noise I'm hearing is totally normal? I'd be interested to know what the rest of you think. One other noise that I'm pretty sure isn't normal is a rotating knocking / thudding noise when going around roundabouts and tighter corners. Weirdly it feels like it's coming from the front of the car but mine is a C2 so I can't think of anything that would make this type of noise. It sounds like a CV joint or something to me, not that loud but I definitely notice it when driving. My worry would be that the 'gearbox' noise and this rotating noise are related, maybe differential? It's something that I'd like to work out what it is before I start putting money into other areas of the car like suspension.

I’ve got a gear cable alignment tool if you want to borrow it Sounds like that gearbox oil was well passed its use by date. You shouldn’t have any noises really Nathan , there’s something that needs looking at but they can be hard to find. See if you can borrow that lift again, check the gearbox mount and other stuff up front

Mark 2, good choice sir. The Germans haven’t managed to seal an engine in my life time yet I still come back for more. A well sorted 996 c2 should drive beautifully, I’m sure you’ll get it sorted Nathan.