My engine (M104) has 156,000 miles on it and I only have records back to 138,000 miles. Is there any way to know if the engine has ever been replaced? It just seems to be too clean and leak-free for that many miles. The car was out of state until 2004. Are there numbers on the engine that should match the car's serial number?

 

Probably. My car is about 100k miles, and so far (knock wood) its amazingly well running! I think you may just be experiencing a garage-queen plus the engineering marvel of benzo. Hopefully your car is just being friendly as has just aged properly, and did not have its engine replaced.

 

Thats highly impossible. i have a carefully driven 1995 C280 with 103000 miles and its got a head gasket leak, and i think the radiator is about to go out. after 100K miles, there will definitly be leaks in an engine.

 

could also be that the head gasket was done after 138000 but before the OP bought it.

 

Next time you change your oil look for the engine number to be stamped on the block, I believe they are usually under the intake, or on the drivers side. That way you can call it in w/your VIN to the dealer.