Sudden Loss of Compression
 

I have a 1986 300e with 135,000 miles. During my last service, I had all of the lifters replaced (one was sticking and made a loud tapping noise) and also two rocker arms needed to be replaced. Since then, my car has been driving great, but yesterday on the way home as I came to a stop, the engine suddenly started to idle extremely rough, in fact the whole car shook. As I tried to accelerate, the car seemed to have lost all of its power until I got up to around 25mph and then it was fine, that is until I slowed down again.

Today, the mechanic did a compression test and said that one of the piston rings was bad. It was the #1 cylinder and it had a dry pressure of 25psi and wet was 100psi. All of the others were 145-150 ish. He recommended getting a rebuilt engine over repairing it.

My question to all of you is, could it be anything else? I read some posts and I have been losing coolant lately and I looked and there is some oil in the resevoir. Recently, I also had to add some oil after only 300 miles. Could it be a blown head gasket or does the wet test rule that out? I can't believe that the piston ring just broke and I would think that I would have noticed it slowly getting worse if it was due to wear. I need help.
Thanks

Your mechanic is probably right, a broken ring is the most likely cause that I can think of.

Sudden loss of compression and high oil consumption do fit the bill of a broken ring.