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Just got the car; drained the oil and sent a sample for testing

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Hi, first substantive post. I've been lurking a lot the last couple of weeks.


About a month ago, I brought a 2001 996 carrera cab / tiptronic home. 164,000 miles, and needs some love. No visible signs of abuse (for what visible may or may not be worth) and no wrecks. Its just been neglected the last few years of its life.


Drove it about 20 miles, half an hour, to get it home - coolant temp normal, oil pressure normal, no CEL. In fact, the only light is the convertible top light, which I know doesn't work. No smoke, runs and drives as I'd expect.


The first weekend I had it, I drained the oil and autopsied the filter. I've documented that more than probably anybody would want to know on instagram, @keith_996.1.


I sent an oil sample to Blackstone.


Blackstone's report says there is too much fuel (2.5 and should be under 2.0) too much potassium (641, universal average of 2) too much sodium (158, universal average of 10) and too much silicon (20, universal average of 7).


So, Blackstone suggests coolant pressure test. Because it looks like a blown head gasket, which would explain the fuel in the oil and the antifreeze in the oil. Except we know the M96 isn't really known for blowing head gaskets, it is more likely to have a cracked head.


Also, for context, there is no visible coolant in the oil. There is no visible or physically discernible oil in the coolant. You know that sickening oily residue feeling on your finger tips, after a dip in the expansion tank? Yeah, none of that. Just looks and smells and feels like oil (from the oil pan) and coolant (from the expansion tank).


Additionally, the expansion tank cap is an antique - an 00 cap that's probably original to the car, first-gen cap, and gurgles like a leaky lunatic after driving just up to temperature.


So I pressure tested the cooling system.


I put 19.5 psi on it, and at 15 minutes it was about 19.2. At sixty minutes it was just below 18 psi. So its consistently dropping about 0.3 psi every quarter hour, which seems pretty normal to me for leakage at the cap, and if I didn't have coolant in the oil, wouldn't suggest anything wanky to me.


Started it up after an hour, no smoke.


So I pulled all six plugs, stuck the throttle plate open, and did a compression test.


Cylinder 1 produced 120 psi, about 13.6% lower than the highest cylinder - that's by far the largest differential. 13.6% isn't anything to be happy about, maybe (?) more so because every other cylinder is within 1.83% of each other.  So #1 really stands out. But a) it is just one cylinder (not two adjacent); b) even 13.6%  doesn't seem catastrophic on an engine that's got 164 thousand miles on it, and c) when I put some Marvel's Mystery Oil in there, it shot up to 150 psi, which I thought (?) is the result of ring seal. Poor ring seal might explain the fuel in the oil, but wouldn't explain the coolant.


Again, though, like the coolant test, I totally wouldn't have any concern about the compression test unless I had a lab report that says I've got coolant and fuel in my oil.


So at some point I'm going to drop the engine and tear it down and rebuild it anyway, but for now I'm thinking I'll replace the expansion tank cap, plugs, belt, and put about 500 miles on it while checking oil and coolant levels constantly, then send off another sample. The only other thing I know to do would be panic-drop it now and tear it apart, I'm just not convinced.




Edited by Keith Upson
Left out a detail. :)
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