Getting a 996.1 with intermix back on the road

Hey everyone. I've been hanging out in the 997 forum as I rebuilt/refreshed a 997 C2S over the past year but I recently purchased a 1999 996 C4 with intermix and 180k miles from @z driver 88t . The car arrived a few weeks ago and I've slowly been digging into it. Any tips/tricks when dealing with intermix are welcome. I'm assuming it's a crack in the cylinder head and I've been in touch with Len Hoffman at Ham Heads for the repair. I have the engine out of the car (pics below) and am starting the process of flushing the coolant system with Shout detergent and a sump pump. It's been about 11 weeks since the intermix so I believe I've caught it before the rubber coolant hoses have been negatively impacted by the oil. Things worth noting: - The intermix is only in the coolant, not in the oil. I drained the oil and it looks clean. Filter doesn't have any debris. - I've scoped the bores and they look excellent, even better than my 997 with only 106k miles. The PO did oil analysis every 5k miles since getting the car @ ~100k miles with great results. - The car had an LN IMS bearing around 107k miles - It is not the original water pump, I'm assuming the water pump blades broke off and contributed to the head cracking but I'll prove this out during disassembly/flushing. The plan: - Leak down test - Flush the coolant system - Send both heads to Len Hoffman for repair/refurbish - A lot of "while you're in there" maintenance (AOS, tensioners, chain pads, RMS, another IMS bearing (maybe?), water pump, thermostat, clutch/fw, and more..) Any advice is appreciated and thanks for following along. This is a well taken care of high-mileage 996 that I want to get back on the road for many more years of enjoyment.

Don't do the AOS. Just trash it and get the uaos. Much easier with engine out and you want that done. Car looks great. Cheers.

A possible source of the intermix may be from the oil cooler.

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Before selling the car the previous owner removed the oil cooler to pressure test it and it was fine so this is unfortunately a bigger issue.

While the engine is out I highly recommend replacing the coolant reservoir tank and fuel filter . It's literally a 10-15 minute job with the engine out , it is a knuckle busting PIA with the engine in place . I totally agree with replace the AOS with the UAOS with track drain with the engine out . Money well spent . Len Hoffman did the heads on my C4 and my 986S . He is arguably the best out there .

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Yes good advice, thanks. I need to replace the coolant reservoir on my 997 and have heard it is a pain. Really wishing I had seen the cracked reservoir and done it on the 997 while I had the engine out earlier this year.

+1 on Len Hoffman. He did the heads on four of my engines. I would recommend replacing the IMS bearing with the IMS Solution if you want to keep the car long term. The existing IMS bearing has 70 K miles on it now and should be replaced. The IMS Solution converts the IMS from a ball bearing to an oil fed plain bearing like the air cooled and turbo 911 engines have. It is a one time retrofit that does not have time or mileage limit. You can replace the 996.1 coolant reservoir with the 996.2 reservoir which is much less expensive. Only buy the coolant reservoir from Porsche dealer to be sure you get a genuine part. It is very difficult to change with the engine installed and all the non-genuine ones seem to fail rather quickly. I would also use a genuine water pump from a Porsche dealer. I have bought a number of them from Sonnen Porsche in Marin CA and always received excellent service. I change the water pumps on all my cars every 3-5 years, they are cheap compared to consequences of a failed water pump. Good luck with the work. Mark

can't wait to follow along - anything special with your quickjack setup to allow enough space to get the engine out?

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I actually wasn't able to get it out without removing the intake manifolds. I forgot to use the additional 3" blocks that came with the quickjack so I was about 3" short of being able to just slide it out. Even with those 3" blocks it would've been tight. I think a lower profile hydraulic table might be the solution - like one of these that sits only 4" off the floor when fully collapsed opposed to my 11" fully collapsed table from Harbor Freight.

I don't think "Shout" will clean up that mess.....you have got a ton of oil in the cooling system.... You may need something stronger like brake cleaner/mineral spirits/ect.. Porsche had a special cleaner just for that issue, but it was expensive..

The latest quick jacks (that go higher than the originals) with both rubber blocks will let you pull the engine without removing the intake�.. using the motorcycle jack linked above, or the identical one from HF�� (since we dropped the engine/transmission together, also used an HF transmission jack) -Eric

In the process of flushing the intermix from the front half of the car. I used a sump pump with shout detergent and hot water in a 5 gallon bucket. So far I�ve gone through about 20 gallons of water and it�s all coming out clear now. Next up is the heater core loop and the engine block. Here are a few pics to show the progress.

Progress has been slow but I have located the crack in the head. It�s on bank 2 cylinder 6. Len Hoffman told me the most common place for these to crack is the 5th exhaust guide bore to the spark plug hole (counting from the timing chain) and that is exactly what happened here. The heads will be heading to Len in the next week or so and will be getting new valve springs while they�re at his shop.

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Don't be surprised if Len recommends all new valve guides as they are a common wear item on the 996.1 and seem to always get replaced when heads get done. Its a good thing. Also, a nice valve job while heads are at Lens seems like a no brainier imho. As power/efficiency/smooth running comes from great sealing heads. Not saying you need to go whole hog and get heads ported, but.... If it were mine, I'd do a few final flushes with some dawn detergent mix, and try to reverse flow it a couple times. Dawn is the best at cutting grease/smegma imo. As that smegma is poison on the rubber hoses and will cause them to get soft and pop down the road depending on how good/completely system is cleaned out and how long the smegma stayed in there soaking into hoses. And from your posts here seems car was bought as a intermixed basket case so might be hard to tell how long the smegma was in there.? Might want to take the radiators out and clean/flush them individually then back flow/flush thru the open hoses/pipes back to engine. Hate to pop a hose and lose all coolant at speed and overheat the engine again. Imho, from your pics, the amount of smegma you had/have in the cooling system for an undetermined amount of time, its probably best fixed by installing all new hoses after the system is totally cleaned out of the smegma intermix milkshake. . Anything less is a probably a gamble. jmo

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that seems to be conventional wisdom. Considering how far you're going and have come, and the apparent lack of rush, seems prudent to replace the hoses

Hello there, just wondering if there's been some updates on your car? Just bought a car with similar symptoms this week, we're assuming cracked cylinder head of course. Ours is a 1998 base Carrera with about 75,000 miles.

Yes there has been some progress. The heads were sent to Len Hoffman at Hoffman Automotive Machine in Georgia and he got them all fixed and cleaned up. New OEM valve springs, new valve stem seals, new expansion plugs, heli-coil all exhaust bolt threads. The heads came back in late January and now I need to order the rest of the new parts and start putting everything back together. Hoffman did an excellent job getting the heads cleaned up and the turn around time was impressive. Here is a picture showing how clean and shiny the heads came back. Best of luck with your new project trassalpl

Looking good, thanks for sharing! We'll be outsourcing the dropping of the engine and cylinder head work (+ accessories). We'd love to do this ourselves (bought the car with a friend), but Paris isn't a city that lends itself super well to wrenching on a car, so we'll do the lighter jobs. Anyway, don't want to derail your thread. Looking forward to seeing your car running again!

Maybe also replace the oil filler tube proactively while the engine is out. Which Quickjack model do you have? I didn't realize a Quickjack will get the car high enough to drop the engine.

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Yes the list of items to replace is very long at this point and it includes the oil filler tube because it cracked in half already when I tried to gently move it out of the way. These are the QuickJack 7000 TL. You need to use the QuickJack spacers and a motorcycle jack to have enough clearance.