Mercedes-Benz W201 timing chain and chain tensioner
W201: how long does the timing chain last and how is its condition checked?
The timing chain often lasts hundreds of thousands of kilometres, so replacing it preventively is not always necessary. Its condition is found by measuring the stretch with the valve cover off: the timing marks of the camshaft and crankshaft are read, and the stretch shows in degrees.
W201: is the timing chain single-row or double-row?
The M103 has a single-row chain, and the M102 used a single-row chain until about 1988. You can see it through the oil filler cap opening, where the camshaft sprocket is visible. A single-row chain has no tensioner sprocket; instead the tensioner presses a sliding rail with oil pressure.
W201: what must be considered when assembling the chain tensioner?
The tensioner is disassembled and assembled one part at a time according to the instructions, and its pin is released before assembly. If the tensioner is left too tight, the chain whines and the camshaft can break in the worst case. The tensioner may differ between engines, so use the instructions for your own engine. If the locking ring jams, the tensioner should be replaced completely with a new one.
W201: how are the marks set before removing the chain?
The crankshaft zero point is found on the inner edge of the multi-groove pulley, and the pointer on the block indicates the degree figure. The camshaft mark is aligned with the mark on the cover; if they do not match, the crankshaft is turned one revolution. Before starting, check that the marks of both shafts are in place.