Bought my 9th Mercedes, but made a classic mistake. Been kicking myself as I of all people should know better, didnt check compression. But whats done is done, pity party is over, time to move on.

Number 3 cylinder has almost zero compression, only about 20 psi. Oil does nothing. With both valves closed I can blow on the test adapter and easily blow air into the cylinder without restriction and can hear it in the crankcase, so I know there is something very wrong with the piston.

The question now is, what to do with it? The car is real clean, most everything works, it drives really good, transmission is tight, overall its a very good car. But the mileage stopped at 117K, and it appears that was quite a while ago, so mileage is unknown. My gut says dump the car or part it out. Right now the car runs and drives, someone could drive it home a very long ways, or at least drive it to test the transmission. Once I pull the head, if I find something nasty, its all over.

OTOH, I could get lucky and find its just a bad piston. I wouldnt be opposed to putting one piston in it and drive the wheels off the car. Yeah I know how to do the job right, replace everything, rebuild the head, yada yada. But these things are a dime a dozen now, and its just throwing money away. I could buy another one of these for what it would cost to fix this one "properly".

But just a piston and headgasket, sump gasket, that would be cheap. And God knows, I'm cheap.

Opinions?