I brought my car, 1982 300SD, to my mechanic for a valve adjustment. While cooling the engine down with the valve cover already removed, he noticed that my camshaft sprocket was installed incorrectly. It was inside out which made the chain misaligned and already ate some part of the engine block. It's been like that since I bought it 3 years ago.

He decided to fix it by removing the tensioner and the front covers including the vacuum pump and cautiously reversed the sprocket. I asked him if it I needed to change the chain since it has already rubbed with the engine block and it might already be brittle. He said that they usually just reverse the sprocket without any problem whenever they encountered a problem like this. He then put it back together and proceeded with the valve adjustment.

Engine fired easily and I noticed it to be quieter and the minor engine shake disappeared. We decided to do a test drive together and as we went out of the shop, i stepped on the pedal harder than usual and we heard a pop. Engine died and we coasted beside the road. Turned out later that the timing chain broke and so did the camshaft, one camshaft bearing, etc.

I was speechless when I saw it after they removed the valve cover. I was so down when I left the shop thinking that I only went there for a valve adjustment and suddenly this happened. I still don't know if they will shoulder the repair or tell me that chains do break and they are not to blame. What could have gone wrong?

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