Problem & Solution
Common among these chassis:
W107 W108 W109 W110 W111 W112 Sedan W111 W112 Coupe W113 W114 W115 W116 W123 W124 W126 W201 Classic Sedans Ponton
WARNING: Timing chain failure is the NO. 1 cause of catastrophic engine failure in these old engines. If it lets go the valves will hit the pistons. If it comes off at high speed, the pistons can be damaged and the camshaft can be driven right out through the valve cover!

CAUSES: There are a number of reasons for excessive chain stretch / chain failure.

Age: Just imagine what is happening to that chain as it spins in your engine at 4000 rpm. Timing is everything and the chain is the key timekeeper. At some point they just wear out no matter what you do to maintain. If you have an engine with a chain that has already gone 150,000 miles replace it for peace of mind and financial security.
Lack of Service: Given good oil change intervals, timing chains can last from 120,000 to 200,000 miles before requiring replacement. I have seen lack of oil changes cause them to stretch beyond useful life within 80,000 miles.