Checking it and adjusting it are two different things. Checking it requires only removing the valve cover. After you get the valve cover off set the engine to TDC by looking at the crankshaft at the front of the engine. There are markings that go -30, -20, -10, 0T, 10, 20, 30 on the crank pully (aka harmonic balancer). TDC is 0T. It takes a 27MM socket to rotate the engine on the crank pully. I replaced my spark plugs at the same time and had them out, which simplified turning the engine. Once you get the engine to TDC look up on the head, just behind the camshaft sprocket. There's a cast raised ridge on the #1 rocker arm carrier that aligns with a small hole (1mm?) on the camshaft. Now that you've identified the alignment markings, rotate the engine clockwise one full turn until the markings on the cam line up. Completely ignore the setting at the cranshaft pully until the cam is perfectly aligned. Only rotate the engine clockwise because there's a small amount of slack in the chain and you want to keep the correct side under tension. Once you're happy with the cam alignment take a look down at the crankshaft pully. Between each of the 10 degree marks is a 5 degree separator. I set mine to exactly TDC and it was about 10 degress off. It made a huge difference in the lower-end power.


Adjusting it requires removing the top timing cover. Check out my article on resealing the top timing cover on the M103 engine. After you've got the top timing cover off you need to remove the chain tensioner. This is the large allen plug (10mm?) on the right side of the engine (passenger side in the US). It's spring loaded, and then you need a huge allen wrench (17mm?) to remove an internal collar. The tensioner is extracted by coaxing it out with a scrap bolt. The tensioner is telescopic with a ratcheting mechanism. Once it is out you need to reset it by pushing the inner piece all the way through and then restarting it at the other end. Hard to describe without pics. This is pretty straight forward but it needs to be reset correctly prior to reinstalling it.

Now you're ready to make the adjustment. I'm not sure where the breakpoint is, but in the earlier M103 there's a half-moon key on the cam that can be replaced with one that has a set amount of offset, and they come in 2 degree increments. The later M103 is adjusted by removing the three torx bolts that secure the camshaft sprocket and flipping the sprocket around to have the other side facing the front. This changes the alignment by 3 degrees. I moved the chain by a single tooth and then back 3 degrees to get mine set properly.

__________________
89 300te 222,222
92 300e 190,000