M112 engine humming noise when cold
My C240 (M112) engine recently develops a strange humming noise when it is is cold. As long as the operating temperature is below normal, the engine makes a humming noise when the car is travelling between 25mph and 40mph. The noise appears to be coming from the left side of the engine. Once the engine reaches its normal operating temperature, the noise disappears.
I took it back to dealer, and the dealer could not locate the problem. The worst thing is that they told me this is normal. I think they just could not diagnose the problem. I told them the noise was not there before, but it does not appear that they care to investigate the problem further.
I appreacite if anyone could offer any advise on this problem.
38,400km (24,000 miles)