OM642 Timing Chain Lessons Learned

I share the basic approach for replacing the timing chain on a Mercedes-Benz OM642 engine highlighting the lessons learned.

I had some ticking noises, checked my tensioner and found out it was fully extended. This meant that my timing chain was stretched. This is a common occurrence on the OM642 engines, and it had to be replaced. When I exposed the timing chain and sprockets under the right-side timing cover, I found that the valve timing on that cylinder head was retarded a full fifteen degrees.

Thankfully this chain can be replaced without removing all of the accessories from the front of the engine and the timing cover. By pressing one pin out of the chain, one can connect the new chain to the old chain and turn the engine over by hand until the old chain is out of the engine and the new one is in it.

From the lessons learned, if I have to do this again, I’ll certainly:

  • Build a tool that would go into the cam holes where the timing cover meets the head and press them apart, so that I’m not banging on things and stripping out threads.

  • Buy a better tool for the temporary link.

  • Modify the chain tool so that the process of pressing pins and links in and out of the chain can be done without removing the camshaft from the engine multiple times.

See the video for more details.

Have you done this job yourself or paid somebody else to do it? I’d like to hear about your experiences!

The Art of Diesel
The Art of Diesel