How does anyone know when to have their timing chains changed besides guessing on the need to have it done based on mileage travelled like 100,000kms, 200,000kms, 250,000kms, 300,000kms ?????

It would be risky to wait until it breaks! Then what? There will be lots of damage costing tons of $$$. So is it true that you have to open the top before examining the chain and guides to decide? Then you will also have to change a new gasket.

Five years ago, I purchased a 1989 420SEL, my first Mercedes. At that time I purchased a full set of Mercedes manuals and started looking at the Mercedes Owners groups web sites for problem areas. My attention was zeroed into timing chains and what happens when they break; there were horror stories. I decided that I would not chance a break. I ordered the chain, got a friend to help me, and installed it in my V8. Before installation, I carefully measured the length of the new chain. My replacement procedure was to remove both valve covers in order to expose the cam shaft drive gears at the front of the engine. I then used a Dremel tool grinder to remove a pin in the chain linkage, attached the new chain to the end of the old chain, and turned the engine with a wrench to the crank shaft pulley nut, and wound the new chain right in and then bound the ends of the new chain with a link. I also replace all guides available to me from the top of the engine.

Now, was it necessary? The car had 150,000 miles on it when I did the work. After removal of the old chain, I carefully measured its length and compared it to the new chain length. I found no difference in length which meant little or no wear.

Following all this effort, further study concluded that the chain problem in the 420SEL existed only in the early models which had only a single wide chain, while the later models, such as mine, had a double wide chain which gave no problem.

I hope that this may be of value to you.

BigCar

Hocky:

I'm not sure what model you are enquiring about and your profile doesn't indicate what model(s) you own, but the answer is nearly the same anyway. I would do a search on the subject and review what has been said in the past.

Basically, the chains don't stretch. They elongate with wear (double chains included). There are methods for checking the amount of elongation based upon where the timing marks are when the camshaft is in a given position. If you hear the very distinctive noise of a broken piece of chain, it needs fixing immediately. The lesser problem of elongation usually makes itself known by a reduction of power (because the cam timing is late).

However, on those vehicles using timing belts, a replacement schedule makes sense.

My $.02.

Wes

For the old American muscle car V8s, the method of checking the timing chain was to rotate the crankshaft back and forth while watching the distributor rotor. If there was more than 10° slop, time for a new chain. I'm not sure how or if this method can be applied to MB engines.

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95 E320 Cabriolet, 159K