I brought in my C350 into the dealer last week for the 1K-3K mile check. I also had a concern about a pinging noise coming from the front engine area. Sounds similiar to what an engine would sound like if you used a low grade octane gasoline in your car. Anyways, it turns out that this has been an ongoing problem with the 350 engines. As most issues with MB, it takes a while to build up enough data to determine the root cause. It is the oil pump. It has just been recently that MB has decided to change out the oil pump. So just a heads up.

The problem on my car was it only occured at cold starts and goes away within 5minutes of driving. If you hear this noise take it in to your dealer. At first they did not acknowlege it. As a result, I went to pick up the car the next morning. Once I started it and the head technician heard it he knew what it was.

This is not a recall. You have to prove your case.

 

It's not just the 350, it also happened to my 300. I thought the dealer was feeding me a line of BS until I read your post. The car sounded like it was a diesel for the first 5 min in the morning. Lame! Would you believe that the dealer said they couldn't replicate the problem at first. Lamer!! It took two visits for them to hear it.

 

this basic engine has been around for a while - is this some endemic problem or just a run of bad pumps in their supply chain? maybe they are using pumps made in china.

 

That's what I said to the service advisor when he tried to tell me it was because it was a new design ???

I think it must be a bad batch of pumps. Of course the cars that they tested for 30000 miles at redline didn't have the issue....

 

My Tech told me that they redesigned the pump and are replacing them as people *****. New cars have the new pump. This will be the last V6 I buy from MB. I have owned only V8s and the V12 bi-turbo and they all seem to be well built. At least I never had problems with any of them.

I have owned MBs for 15 straight years and to tell you the truth I don't know if I will get another.