Replacing timing chain 996 - split case ?

M96/3 3.6 engine I have some timing error codes on bank 2 and initial investigation suggests timing chain slipped a tooth and/or broken. Have not scoped yet but from quick look after removing cam plugs, intake and exhaust cams timing off. Vehicle not driven since issue occurred. To to move forward I am going to have engine inspected by my indie. When replacing a timing chain, I assume case must be split as chains continuous without master link. Is that correct ? Just want to know what to expect other than damage found from valves hitting pistons etc. I am aware sprocket on IMS may be damaged. Any good links to rebuilding an M96 for my education ? thanks.

There are master linked timing chains from IWIS that can replace the stock chain without splitting the case. They should be available from LN Engineering

Ashai Read your complete rebuild thread. You are a legend. However Jake will no longer sell them as he wants to keep them for his builds. He reasons he put the work in to get them made and they are in short supply. Even if it could be done is it even possible to inspect IMS sprockets without splitting case ? as I am sure you know, the videos are thin on this. The ones I can find are timelapse. Most of the links in your thread including ones inn flat6 no longer work. Thanks. David

You can turn the crank and see if and how the cams follow. If the cams don't follow, then the IMS sprocket for that bank is definitely slipping. If that's the case, the valves will be bent and cylinders not firing. Sounds like your engine was still running though. What codes you got and is the timing off a lot between the cams? Did you just get this car? Any history? It's unusual to have a timing problem if the timing has been fine.

Ahsai Full background 03 C4S with 58k miles. Original engine replaced by Porsche with crate engine in November 2009 at 38,000 miles. Replacement is a reman and a M96/3 with the oversize single row IMS. I bought in 2017 and immediately had transmission dropped, IMS bearing inspected, carrier replaced, RMS replaced and clutch done. Per Jake and others, outer seal of stock IMS bearing removed. Since this time I have been running Motul x-Cess 8100 5W-40 changed every 6 months. Fast forward 1500 miles and I decided to change battery for a Bosch AGM. Old one was getting lazy. Take it for a long hard run and come back and get really rough idle. I guess (wrongly) it was due to adaptions after battery change so re-initialize everything and go for a run. Feels like its a little sluggish and not crisp. Get some pending codes, Multiple Misfires bank 1 according to generic reader. I then get a hard code. PL 0022. Cam over retarded Bank 2. After some research and finding diagnosis manual for PL 0022, I remove and clean the solenoid for cam timing on bank 2. After I replace, initially idle cleans leading me to think issue is with cam phaser or solenoid but after a run its poor again. I replace solenoid with new genuine one but no improvement. I get a Durametric and find Bank 2 running around -7 degrees and bank 1 -1 degrees which is right on the edge of acceptable. However, bank 2 exhaust (Driver side) louder and rougher than bank 1 seemingly confirming cam timing stuck in wrong phasing as car runs fine over 3000 rpm. Decide to take to my Indy. Go to start and as I hit key, I feel a small bang and engine stops instantly. I do not try to restart. I then decide to turn engine over with wrench on crank pulley gently and it feels quite normal however, I removed cam plugs and inlet and exhaust cams bank 2 clearly not timed correctly. I decided NOT to turn engine over any more and had it trailered to my Indy. He is a bit slow but told me they scoped it and can see marks in top of piston on #6. That is where we sit sadly ... David

Sorry to hear that and it does sound like a IMS sprocket issue. By "marks in top of piston" I assume you mean the marks left by the valves while hitting the pistons? Do you use a spin on filter? May be good to drop the sump plate to check for any debris. Since the cams are still rotating with the crank. it does sounds more like the sprocket(s) slipping, which will need to be addressed by splitting the case. Keep us posted and hope the damage is limited.

Oh regarding engine rebuild documentation, the free 996 workshop manual has pretty good documentation of the 3.4L rebuild. The procedures for the bottom-end is almost identical to the 3.6. The heads and cams are obviously different so is the timing procedure. You can't use it as a step-by-step to rebuild a 3.6 but the amount of details is enough to give you an idea what is involved. https://rennlist.com/forums/997-foru...pplements.html

Is it possible the IMS sprocket has spun on the shaft? I believe factory they are friction welded or pressfit, aftermarket drill and pin the sprocket to prevent any chance of it spinning.

Quotes source post: 15903173

Very possible !!! It would be great if someone would build an internal "expander" to insert into the IMS to apply about 10k lbs pressure at the gears to expand/lock the tube to the gears. It would make it unnecessary to pin/weld the gears and could be done without splitings the cases..

If the motor was fairly quiet,, I would lean towards the slipping gear, but if you touched a valve,, just pull it, bare minimum that set of valves needs some micrometer run-out checking.. And its really unlikely that only one hit, if it is only one buy a lottery ticket now.. Good luck.

Subscribed - sounds like this will be an interesting challenge but OP you sound like you're pretty clued in

I will try to document as much as possible. My Indy was good with pics for the IMS inspection etc.

Ok all, After talking with 3 local specialists, I have been told to expect $8k to $10k in labor plus parts. This puts me squarely in the uneconomic to repair camp. I have a face to face with my preferred Indy next week. However, my thoughts now are that I should do this myself. I am ironically currently building a standalone 14' x 24' garage which I plan to put a small lift in (48" max lift). It will have power and plenty of space. I have experience of building older V8s and some overhead cam VW 4 cylinder motors. Am I mad to consider taking this on as I am told "this engine will try to kill you" David

Quotes source post: 15904911

A few people on the board have rebuilt the motors and they run fine. U may want to invest into the i internet and in person class by Flat Six. U can always find a donor motor and swap it in for a little less.

I am definitely looking at courses from Flat6. David

You're not mad - i'd do the course and then tackle the rebuild - I think time is the factor. I'd dive straight in!

Time no issue other than missing a summer to drive it. The satisfaction of doing that myself would be immense.

Quotes source post: 15906178

Go for it - you've got the forums tick of approval and support! (Moral from me!)

Ok, We have moved on. The shop that has it have definitely told me Bank 2 cams both rotate with crank but out of time (retarded) by "more than one tooth". They are now on hold waiting for my decisions. It is worth noting that they told me if they do strip both sides they would prefer a replacement short engine as cost to assemble is high due to hours involved/individual parts purchased. My original plan was to get it back on the road this summer but now I am thinking that is leading to bad decisions. My options are: * Have them strip and rebuilt all issues related to bank 2. This will be $7500 or so but not giving me any long term security as engine not gone through. * Have them strip and rebuild both banks and replace all timing gear and any other wear items. This will be $15-$18k based on current estimates. * Pull if from them and pay for what they have done and put it in garage. I am building a 24 x 14 standalone garage with a lift that will be finished September ish * Drop engine myself and either send out long motor to RMD (now run by LN) as it comes with all fixed , upgraded parts, ARP goodness etc but takes 5-6 months. Cost is high but likely only chance of me ever relaxing and trusting the motor ever again. This will really push my cost tolerance .... see below ... or pull motor and rebuild myself with all same good parts. Cost better but by time I buy parts, have machine work and buy tools we will be close to RND. * Drop engine and replace with used engine (dressed) at cost with warranty ($8k ish). This could go one of two ways but is cheapest option and leaves me my motor to work on while I drive and enjoy. A local Porsche Dealer I have a connection with has done this quite a few times for people like me and having good success for people who had considered walking away. However, I am very concerned about throwing good money after bad even when using known Porsche breakers ***insert 'ebay engines are a huge waste of money' comment here. In all this the labor costs seem to be the big deciding factor so if I can wait and accept next year may be first time I drive again, it makes several options manageable. In all this the sad fact is that my upper cost limit is right at $15k before it becomes unacceptable but with the car being worth perhaps $5/$6k that is all I can really afford. I will keep you all posted David

New Porsche Short Block for $7K!

Quotes source post: 15918066

I hear ya but this is second genuine Porsche assembled engine in this car. First failed in 2009 with IMS and crate engine (reman) installed by Porsche. This has now failed inside 20,000 miles. Hence you will forgive me if I don't trust Porsche reman's anymore... David

I would do the RND or build myself. If you can't afford the RND now then save for a few months. If the other options are ~$4000 then I would do that but given that it's $7000 to $15k it seems the risk / reward is to low.

Quotes source post: 15918229

I am working out if I can do the RND option. They are saying they will be doing kits soon but I think if the cost spread over the 6 months from deposit to delivery I may be able to make it work. It does mean I will never get anything back out of the vehicle which means I will have it a long time ... David

Quotes source post: 15918240

Let's say you bought the car for $20k and have to spend $15k on the RND, that is $35k for a pretty nice car still. What else can you buy for $35k? Mustang, 370Z, a BMW, Fast Civic, Fast Ford Focus, etc.

Quotes source post: 15918214

I missed the reman with 20K part.

Quotes source post: 15918263

Its a good point but after I bought at around $25k (it�s very very clean) and inspected IMS and found it to be the oversized single row, I put around $5500 into it with clutch, suspension, bushings, shifter etc. engine from RMD currently $17k I have discovered so we are now pushing $50k which changes the math considerably. If I had bought the Turbo in 2017 that was $20k more at the time I would be ahead ;-)

If the engine only has 20k miles on it, and it were my personal car, I would dissasemble the engine, pin the IMS, check for runnout, replace any bent valves ect, reassemble and drive..leaving out all the "while you're in theres"...

[QUOTE][ If the engine only has 20k miles on it, and it were my personal car, I would dissasemble the engine, pin the IMS, check for runnout, replace any bent valves ect, reassemble and drive..leaving out all the "while you're in theres"... /QUOTE] ^^^^^^ +1

[QUOTE=OutNSpace;15918564] Thanks, This is an option, however, we still don't know what caused the issue. I would have to inspect the bearings at the very least but I am open to suggestions from those with experience. As a point of reference, oil pressure always very strong up to this point. David

I don't want to give you false hope but one possibility could be a bad variocam+ phaser or the phaser big bolt has slipped (as opposed to a slipping IMS sprocket). You will need to do a closer and more precise inspection but if true, your repair cost will be drastically reduced. It may be worth diagnosing it more yourself first before considering a rebuild.

Quotes source post: 15918778

Many thanks. I have considered this. Given that I now don�t have any rush to get it back I may pull the car from the Indy and store it until new garage complete. Then I can diagnose slowly and methodically without any time or labor cost pressure.

Quotes source post: 15918871

Exactly.My guess is if you unbolt the engine mounts and lower the engine as much as you can, you should have enough room to remove the cam 2 cover in-situ, then remove the cams and the phaser for inspection. If it's really the IMS sprocket slipping on bank 2, you will need to drop the engine to replace the IMS. The cases I saw online when the sprocket is slipping. usually the cams don't even move with the crank.

Quotes source post: 15918917

Can you think of a scenario in which both inlet and exhaust would have retarded timing if the phaser failed ? I have not seen it yet but I am told both are off. With a 3 chain engine I can see if chain slipped this would happen and this implies lack of chain tension and failed tensioner and or ramps thanks. David

Quotes source post: 15918926

Yes, agreed I was hoping the cams are not retarded by the same amount (say intake retards way more than the exhaust).

Asahi Don't you think this could be a cam deviation between the two cams in the head, rather than a main timing chain slipping out of time ?

Quotes source post: 15919002

No because the OP said it's a reman'ed engine and has been running fine for a long time. So I assume the engine timing was correct before. The OP seems to indicate now BOTH cams are retarded by same amount. If only the intake cam phaser has slipped, the intake cam should be retarded but the exhaust cam should remain in time (because the timing chain governs that and assuming the orginal timing was correct).

A word of caution: We had a technician at the shop rebuild an m96 5chain after an IMSB failure that had also jumped time. He had inspected the IMS and checked runnout and tested the gears for slipping by trying to turn with a chain wrench, he said he couldn't make it slip and reinstalled the IMS with new bearing. After about 15min run time he reved the engine , and the IMS gears slipped on the shaft. He had to do it all over again. Moral of the story, the gears may not slip easily and may be hard to verify, when in doubt PIN THEM..

I think the minimum is to remove the bank 2 cover and inspect the said components. If nothing obvious on the tensioner and cam rails, the problem is likely on the IMS sprocket end.

One of the problems right now ,, is EVERY noise/fail etc is a "IMS" fail,, (I'm guilty!) I'ffn it was me,,, Since you cant run the motor right now, the car is a roller, so your as down as you'll get. I'd tear it down myself, see if there are any obvious real broken bits. Worst case buy a rebuilt case set from you favorite and have the fit the pistons if you bump the displacement New cam chains, new guides and a pinned IMS. new set of main and rod bearings, just have the cams checked for run-out, if the lobes are good then leave all the top end except pop for a good valve job.. new valve seals and maybe the vario cam actuators. Have the crank polished. In most major cities, there is someone who can do the assembly,,, some will do a house call for a reasonable amount when your ready to hit the hard parts.

Quotes source post: 15919023

Standard comments, it was running great just until it didn't ! :-) Yes, strong performance and 1500 miles since clutch job and IMS inspection. I still have a nagging feeling that when the Indy shop checked the IMS, they either re-installed tensioners incorrectly or somehow let timing slip. It would be impossible to prove however. David

Quotes source post: 15920239

If the shop messed up the timing, it should have shown up right away and not 1,500 miles later, right? You can visually check if the tensioners were accidentally swapped. They have different number of rings marked on them.

Not to sidetrack this but, is there a way to confirm the tensioners are up to snuff?

Quotes source post: 15920827

You read my mind. Anyone ??

Quotes source post: 15920827

You can pull them and check the o-rings for damage, check for spring collapse, excessive slop/wear of the plunger. The tensioners don't usually fail all at once ( but it's possible) they usually get weak and you can hear the chains slappin a little.But as always unless your confident in them , replace them..

Quotes source post: 15921461

Vehicle on its way back to my house. Any point trying to lock cams before I do this even if I can (I expect not due to retarded timing ) Thanks. David

I could be wrong but I think you need to lock the cams or pin the crank before pulling the tensioners.

Quotes source post: 15921623

Yup. But with cams being so far out of time I doubt I will get the tool in. David