Hi folks,
Bought a 2004 996TT 6-speed Cabriolet and noticed early on that it was losing coolant, sometimes quickly (almost a gallon over a few hundred miles), sometimes much less quickly. At one point I noticed it leaking under the car, near the center, out from the large black undertray seam, pretty fast, drove it home to diagnose and it had stopped by the time I got there, though the coolant level was appropriately low. This hasn't repeated since, which is immensely frustrating.

I took it to my brother's shop and we put it on the lift and found what looked like dried coolant on the heater core circuit hoses towards the back of the car (yellowish powdery gunk on the hoses and pipes) but no other evidence of leakage. We pressurized the system and it held OK and we didn't see any leaks. We drained and evacuated the cooling system and refilled for good measure. The coolant was clean - no oil in it at all. The car doesn't produce white smoke on startup, and the cooling system doesn't seem overpressurized at all when it's hot - I can take it for a spin, then get home and remove the coolant cap on the reservoir and it releases pressure, but nothing excessive. I drained the oil from the crankcase to see if there was any coolant in it. There was a small amount of water (maybe two teaspoons?), but it was clear and I didn't think it looked like coolant and thought it was maybe condensation. Drained the oil from turbos and oil tank also - no coolant or water at all in either of those locations. Oil filter looked normal - no foam, just black oil. Replaced filter and refilled the oil and drove around a bit, then decided to pressurize the cooling system for a long time with a pressure tester. I pressurized it to 20psi and it lost ~4 psi over several hours BUT I also noticed I was losing coolant to somewhere! No coolant on the ground, no visible leaks anywhere, so I drained the crankcase again and this time it was obvious - definitely coolant in the bottom of the crankcase - a cup or so this time, and coolant-colored. Crud. I have a video of me pulling the plug but it requires a parental advisory for explicit lyrics

I've noticed that I don't really lose coolant WHILE driving... I tend to lose it after I park the car and the car is sitting there with pressure in the cooling system. I honestly wonder whether I wouldn't lose coolant if I just depressurized the system every time I turned the car off. I recently drove it almost a thousand miles in a weekend and lost only maybe a cup of coolant.

I'm thinking this isn't a head gasket failure because then I'd see cylinder pressure in the cooling system, yeah? Is it possible this is an oil cooler failure? Any other ideas? I'm prepared for the fact that this may be "engine rebuild" but I haven't seen anyone with these exact symptoms before. Thanks in advance for any ideas/advice.

 

Post it on Rennlist

 

Thanks, I'll give that a try.

 

Any update, How is everything going?