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Thanks to everyone who has provided assistance and guidance with my 2001 996 Cab project. The car did have a crack in the 1-3 cylinder head which was allowing oil and water to mix. I sent the heads to Hoffman Machine in GA, they were fantastic, I highly recommend them (thanks for the suggestion). Heads are back and reassembly is going smoothly, but for one curious question. Above the chain slider on the 1-3 bank is a small metal baffle plate fastened with a short 10mm bolt inside the head. You can see it above the chain slider and cam chain in this pelican parts photo immediately to the left of the left most cam journal on the intake cam (see below). My question is an odd one - is there no identical baffle to be installed on the 4-6 bank? I was quite careful storing all the bits that came off the engine and cannot find it. FWIW, the 996 parts fiche suggests that only one of these is installed in the car (heat shield 996 104 233 01). The Bentley manual suggests this part is only needed for the left side (1-3 bank), but this seems somewhat illogical for a Porsche (and I have found errors in the Bentley manual elsewhere). Is it true that only one of these is needed?
I did get both heads off yesterday, pretty easy, actually. No visible cracks, but the AOS vent line to the 4-6 bank is filled with oil / water intermix. Weird. I cannot pressure test the head myself, so will see what Hoffman says. Actually, cam journals, bores, combustion chambers, etc all look really good for a 130,000 km 2001 car. No scoring, all pretty clean, not much carbon build up. Now to build those shipping boxes...
Thanks, that thread is pretty hard to follow - is there an actual product there, or just a suggestion to seal an atmospheric port on the OEM AOS? I will be replacing mine in any event, along with hoses, oil cooler, etc.
johnmh replied to johnmh's topic in 996 Series (Carrera, Carrera 4, Carrera 4S, Targa)Thanks, I had done that job about a year ago last time the engine was out. Those sliders were really worn. I got the 1-3 bank head off this evening (no obvious cracks), 4-6 will come off tomorrow (which is full of crud, so I suspect I will find a crack there). Then to find some quality packing materials... Hoffman will get my heads too.
Hi, I am taking my heads off my 3.4 to get them checked and at least one crack welded. To remove the head on 1-3, I set the crank at TDC cylinder 1 and remove the head. Easy. I can use zip ties and paint marks to check the timing does not change. To then remove the 4-6 head, I assume the crank can stay at TDC cylinder 1? I do not need to rotate it 360 degrees to set cylinder 4 at TDC? To do so would be difficult, as the cam chain and gear which bolts to the 1-3 exhaust cam would need to turn (difficult with the 1-3 chain zip tied in place on the exhaust cam sprocket). The Bentley manual is unclear on this point.
OK, so replacing NPG coolant (which runs under no pressure) with straight water in an attempt to flush the cooling system proved beyond any doubt that there was a crack in the head. In short order the 4-6 valve cover developed some oil water mix. So the engine is out and I am about to remove the cylinder heads and send them to repair at Hoffman. Thanks for the tip. Along the way I will swap out the old coolant hoses which were exposed to oil. Should I replace the (1 year old) AOS and oil cooler as well? I want this oil in the coolant issue behind me.
How can I diagnose the crack in a head without removing the engine, both heads, etc.? What percentage of 996 heads crack? If it hasn't yet in 19 years it may not. Even if I have them both welded, they can just crack elsewhere, no? Can I check it with a cooling system pressure check to see if it holds pressure? My current strategy is to flush the system completely until no oil can be found, drive it for a while longer and wait to see if the issue reappears.
No coolant in the sump. Driving also does not seem to consume any noticeable oil. The car did have a failed oil cooler when I got it - there is no question oil got into the cooling system, I replaced it as well as all the hoses. As oil circulates at a much higher pressure than the coolant, there is no question that oil would get into the cooling system. One idea of a local technician I know is that the oil in the cooling system may be significant in amount, but residual from the time spent with the broken oil cooler. He suggested flushing it, repeatedly. I have now flushed it 7 times over 2 weekends, using 4 cans of rad flushing fluid in the process (last 2 flushes with water alone). The drained fluid has gone from red to pink to light beige, with diminishing amounts of what looks like old, dark oil in it (none in the last flush) although a small layer of white foamy scum always settles on the top of each sample. I drive it with the heater on for about an hour between flushes and unplug various hoses to push excess water out, using a compressor each time. I may just try the garden hose until it runs clear and try my luck. All else fails, I think I can pull the cylinder head myself (if I can figure out which one is cracked).
My 2001 996 has been depositing oil into the coolant for some time now. After reading everything I can find on the subject, I suspect that it has developed a crack in one of the cylinder heads which allows oil to enter the cooling system. I am going to get a local shop to help diagnose which head is cracked, any suggestions other than removing and examining both? Car runs perfectly otherwise, so I suspect coolant is not getting into any combustion chamber (a test for combustion gas in the coolant was negative). While not terminal for the car, it seems like a real pain to drop the engine, remove a cylinder head and send it out for welding. Does anyone have a suggestion as to who does this repair well? Ideally, I would be able to swap heads on a core exchange basis.
Just to provide an update, I used a exhaust gas in coolant detection test (great tool), and, after letting the car come to full operating temperature in order to open the thermostat, it passed. Apparently no crack / head gasket failure, which is a relief. My guess is that some residual oil remains in the system (even after a fill/run/drain cycle) due to the broken oil cooler on the car when I got it. I will monitor it and flush it again.
While I wait impatiently for the tool that can check for exhaust gasses in the coolant, a few issues become apparent (if indeed the car has an intermix problem): The issue is not likely to be a head gasket, but rather more likely to be a crack in the cylinder head or cylinder wall. Is there any other likely intermix source? The water pump and AOS are new OEM parts and I cannot see how oil is getting into my coolant expansion tank otherwise. If the crack is in the cylinder head, can it generally be welded, or is the best practice replacement of the head (which may raise other issues as valves, cams, etc, may not cope well with being transplanted into a new head. If the crack is in the cylinder wall, does this mean a new engine? I have $12k in the whole car as it sits, I am not sure I want to spend another $12 k on an engine. I can get a new IMS installed 3.6 locally for cheap from a friend, but the wiring harness and DME transplant issues for use in a 2001 996 may not be practical, and that engine may not come with much history.
Thanks, I will pull the plugs and examine them. There is definitely a mix of something in the coolant tank. As the Evans does not operate under pressure, I suspect if there is a leak, the oil is being pushed into the coolant, rather than the other way around. Car still starts and runs perfectly, nice and cool, with no residue inside the oil filler cap.
So.... I bought a ratty US spec 2001 cabriolet manual with 80,000 miles on it cheap in 2016. Removed the engine and did a deep service, ie IMS bearing, AOS, coils, water pump, coolant tank, timing chain runs and tensioners, belts, just about everything I could think of. I Installed new rads and fans and a central rad just to let it cope more easily with heat. Car starts and runs perfectly, never runs hot, no error codes, just great performance out of my 3.4. So far.... So today I changed the oil (almost none consumed over the last 5000 km and it looked remarkably clean when it came out). I check the air filter (still clean) and then check the coolant level (hmm, about a liter or so below the low level with the car somewhat warm). I also noticed some pinkish vaseline type sludge on the rad cap and a bit more pinkish sludge in the coolant tank. This concerns me. FWIW, I do not use Porsche spec antifreeze, rather I use Evans NPG coolant. I have been using it with success for years in my other, more finicky Italian cars and thought it may be good in the 996. No coolant pressure at operating temperature means an easier life for water pump seals. Any easy way to check for oil getting into the coolant? What are the classic symptoms of the cylinder 'D' chunking? I did notice a slight bit of steam rising from the oil filler neck when I drained the oil , but a really minimal amount. Am I being paranoid? Ironically, I was offered a local 3.6 for cheap last week, but understand the reverse engineering to get it to work in a car designed around a 3.4 is not remotely worth it.
johnmh replied to johnmh's topic in 996 Series (Carrera, Carrera 4, Carrera 4S, Targa)Thanks for the responses. Will look online at Pelican and make a decision. On a related note, after 17 years the suspension could probably benefit from some attention as the car squeaks and rattles a bit on bumps. Would suspension upgrades beyond just replacing the stock parts (shocks, bushings / control arms, springs) which have worn out make sense on a 2001 996 Cabrio which does not go to the track?
I have slowly run out of things to fix on my basket case 2001 996 Cabrio 6 speed. The top now works, the engine runs well, the a/c is cold. It stops, turns and does not leak. So I am looking for my next task. Any suggestions on the best short shift kit for a 996? The current shifter action is a bit sloppy, so I thought about an upgrade.