W124 Valves
 

For a 1988, are the valves on these adjustable? I have a high pitch tapping sound coming from one of the cylinders and it sounds like it is coming from the head. I haven't ruled out anything else yet. If they are adjustable, does anyone know the clearance? Thanks

It's hydraulic.

* David, the valve clearance is adjusted hydraulically by "hydraulic elements". There's an initial setup adjustment (via thrust shims) but no adjustment after that.
* One hydraulic element is located in each rocker arm (M103), 12 hydraulic elements in total.
* The tapping noise you hear might be a hydraulic element which won't "pump up" but rather drains off it's oil too fast. The elements can be replaced without removing the cyl head, but you will have to remove the rocker arms.
* Get yourself the MB W124 dvd or the factory M103 book, if you can find an old one around, and read through the replacement process in detail. You can do some damage here if you mess up cam timing or cam bearing torque. Also keep track of which thrust shim goes with which rocker arm. Good luck.

Robert, to the best of my knowledge the 103 engine has a single overhead camshaft so there are no rocker arms.

David, how many miles on your 1988 vehicle? How long have the hydraulic lifters been ticking? Presuming you change the oil/filter at 7,500 mile intervals you might try some Mobil 1 oil and see if that cleans away any dirt/sludge that may be causing the lifter tick.

Ferdman, The car has 186k miles on it. the tapping started just the other day and it has about 1500 miles on its first oil change with me as the new owner. It sat in a lot for 2 years before I got it in the beginning of the summer. I do know the previous owner did not take care of it well only because of how some things were rigged on the care. I can't imagine that someone would maintain the car properly based on some of things problems I ran into after I bought the car.

Run some "lifter cleaner" through the engine.
Put a few hundred miles on it and then change the oil and filter.
You may have to do this a second time

Wouldn't hurt to final install synthetic oil such as Mobil ! or Castrol Syntec, probably a 5/30 weight.

Also run some Chevron Techron through the fuel tank to clean the injectors and decarbonize the valves.