Worn Timing Chain and Guides

Failure of these chains can lead to catastrophic engine failure

Timing chains have been used on Mercedes engines since the early 1950's. My 1953 220 has an overhead cam six that is driven by a twin row chain - similar to engines well into the 1990's. Timing chains may be old technology, but they are proven and they work for long periods of time (provided the engine receives proper service).

Problem & Solution

Common among these chassis:

W108 W109
W110 W111 W112 Sedan
W111 W112 Coupe
Classic Sedans

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. 
  • Failure of plastic guide rails: This relates specifically to the V8 gas engines but can also apply to other engines. It is common for the upper guide rails to break off. In some cases the plastic can get sucked up into the sprocket and cause the chain to jump timing. We have new upgraded genuine guide rails available along with instructions on how to install them. Don't neglect this to the peril of your engine. For more information see the V8 alert below or refer to my manual. 
  • Poor engineering: For some reason known only to the factory engineers, the 380 V8 engines from 1981 to 1983 were delivered to the US market with a single row chain. This proved disastrous and by 1984 all V8 engines once again had twin row chains. It is possible to convert to a twin row chain, but I don't believe there are any cars out there worth doing it to (even a nice 380SL). My recommendation is that you replace the single row chain every 25,000 miles or sell the car. It is cheaper to upgrade to a new model.