At one point my S-belt shrieked when I made right turns, but only with the AC on. I thought it was the AC compressor turning off under heavy acceleration out of the turn. Turned out my s-belt tensioner was destroyed. Most likely from the local national chain replacing the AC compressor (for the previous owner) and not knowing to loosen the 19mm nut. This stripping the adjustment bolt.
The m103 (and m104) is notorious for oil leaks where the upper and lower timing chain covers meet. Particularly the rearmost corners, both sides. Its a design flaw by MB.
If the oil leak is just above the belt tensioner, at the level of the water/coolant pipe that goes across the front of the engine, it’s the upper timing chain cover. I have that leak now. It was there before and after I replaced my head gasket. I’m going to try to repair it in the next couple days.
The green arrows show where the top timing chain cover sits on the lower cover. The gasket goes under the top cover. The leak will be on the outside (engine’s right, reading left, above the timing chain tensioner) of that joint.
Just do it!
