Hello Everyone, I've been searching the archives of this and the tech forum for a similar problem I'm having. I bought a '91 300D in January and have been very pleased. However, I began to notice a slight ticking noise after the engine warmed up. I checked the oil and the level was correct. I went ahead and had the service done as it was due soon. After the service (done by a Mercedes shop) the ticking got more severe. Again, cold it hardly ticks at all. I took it to a shop near my house and they said it needed and engine overhaul. The car only has 178,000 miles. Not satified with that answer I took the car back to where I bought it. The tech used a stethescope and localized the noise. To me it sounded like a lifter tick. He said it was the timing chain. I ordered a timing chain and tensioner and hope to install it this week. After reading some of the other post I had a question about the vacuum pump. Would a vacuum pump that is going bad be fairly quiet on start up and then get loud? I'm also going to replace the belt tensioner shock as it is also moving a little more than I would like. Finally, I got hold of the Mercedes timing chain replacement procedure. Is the timing marks easy to see? I appreciate any help y'all can give.

Try this,

With the engine running take a screwdriver and press on the top of the belt tensioner shock and see if the noise stops. When the belt tensioner shock absorber bushings fail it can sound surprisingly like lifter clatter.


Did your mechanic check the timing chain stretch before recommending replacing it? If not, PLEASE check it.
As long as the chain stretch is under 4 degrees the chain doesn't require replacement!

Procedure for checking chain stretch
http://home.tiscali.no/henriksen/mercedes/maintenance/TimingChain.htm

Thanks for the response. The timing chain tensioner is run all the way out. So I would sleep a little better if I go ahead and change the chain. By the way, I forgot to mention I get great oil pressure. Thanks for the link.