ftp222

I have a 2002 C230K that has about 21,000 miles on it. A few thousand miles ago a rattling/knocking noise started coming from the engine on start up. To date, the engine still makes this sound, but it only happens if the car has been sitting overnight. The noise only lasts for about a second, but if the car has been sitting for a week, the sound can go on for 4 or 5 seconds. Has anyone else experienced this noise or know of a fix? I know I will have to take it to the dealer, but they will need to leave it sit for a few days in order to hear the sound.

Any help you have is greatly appreciated.

Thanks.

Mike T.

It sure sounds like a loose clearance in a connecting rod bearing (big end) or a wrist pin. The knock stopping when oil pressure builds up is an indication that it's not too major yet, but it could get quite bad over time. Some cars can go on for years without problems like this worsening appreciably. If it was out of warranty I'd say: live with it. But it's not...

I would definitely suggest that you give the car to the dealer for a week and have them check it out. No engine should knock at all, especially one like this. My Peugeot 405 has ~200,000 miles on it and it does not rattle or knock on cold starts.

You should tell the dealer that the knock is unacceptable and you expect them to find the source and repair it under warranty. If they give you a hassle, I'd suggest that before your next oil change, take a sample and send it to a laboratory for testing. The lab will be able to tell you if there are any abnormal levels of metals in the oil which would indicate the likely source of the problem. The lab report will interpret the results appropriately, and that would force M-B to deal with the issue.

I know someone who did this when their car was consuming small quantities of anti-freeze - no other symptoms. Traces showed up in the oil and the manufacturer had to replace the internally cracked cylinder head under warranty in the face of the oil analysis report.

Good luck!

levelr123g

search the forum. the problem is with the adjustable cam positioner ( or whatever you call it). I persoanlly beleive that it is a problem with the hydraulic cam chain tensioner bleeding down overnight. DONT WORRY ABOUT IT its normal. if i remember correctly there is a fix for this that is covered under warranty, but it really doesnt fix it. I still think my theory is correct. the reason for my theory is that when i was working as a motorcycle mechanic, Honda had a problem with the 1995-97 cbr 600f3's engine rattling. the problem was with the cam chain adjuster, and the noise you are experiencing is the same noise this engine was making. the fix was to put a redesigned cam chain tensioner and cam chain follower in the engine. this solved the problem. anyway just my .02 on the theory, but this has been an ongoing complaint with this engine.