M113 Design flaw

 

It is sad to say but no doubt that this is a design flaw of dimensions which in worst case can ruin your engine and if that’s not enough Mercedes Benz has never acknowledged this as a design fault so the grief and the bill is solely on the owner of the car.

 

I am talking about the chain for the oil pump is “chewing” on a tap on the chain cover.

The tap itself is designed to keep the chain for the camshafts on the sprocket so while working on the engine the chain cannot fall of the sprocket and thereby skip a tooth. The chain is running on a clamping bracket made out of plastic which in fact are the chain tightener. This tightener has a spring attached to it …. and when first looking on this problem one should think this spring is the culprit but I think there’s more to it than that.

 

When you “look down the chain” (engine 180 degrees around) you will see the tolerance the chain and tap are given is simply too little. I have not been able to measure the gap but with years of experience inside machinery tell me this is asking for trouble. My first thought when I saw this was that the actual sprocket somehow had been worn down to a small diameter ……. how crazy that sounds ….. since I simply did not believe this very small tolerance was given from the factorySo what to do about this problem? Well – there’s many different ways this can be approached.

 

I will run down the things that come into my mind below – good and bad solutions:

 

• First and the most obvious way are to have another spring made – a much stronger spring.

• Relocate the tap.

• Diminished the tap to quarter or half the size (I have chosen this solution on my engine)

• Remake the tap in harden steel.

• Remove the tap completely. (will make any future work on the engine more delicate)

• Enhance both sprockets. (sprocket on oil pump and sprocket on chrankshaft)