I just bought a 1999 C280 elegance with about 140 000 km on the clock. The car is in an excellent condition and drives like a dream, but noticed something that really bothers me.

At a speed of about 70 km/h I hear a whining noise. Almost sounds like these old sirenes when they used to warn a city of an air attack (not that I really heard these - as seen on tv ). At first I thought it came from inside the car, like the radio or something, but when I open the window one can actually hear it come from the outside. The sound is quite noticable, but not deafening. When I increase or decrease the speed to above 80 or below 60, the noise goes away.

Does anyone know what the source of this sound is?

 

Thats a nice car. It could be any number of things. My guess is it is mechanical, not electrical- perhaps a brake or suspension vibration.
Do you have an independent MB mechanic that you trust yet? Besides finding a nice used luxury car, one needs to find a great independent mechanic. They are around.

 

Jack up the rear end and check out the rear end sounds like a ring gear problem .... see if you free a lot of play in the rear,.... leave it in park with engine off ......turn the drivers side tire clock wise the passenger wheel should turn counter clockwise at twice the speed if you have a posi rear... stop your wheel suddenly and see if you hear a clang that vibrates up the drive shaft. If not see if all the bolts on the drive shaft are tight and that the drive line didn't get knocked off balance .... Like tires sometimes it may do it only between certain speeds have some one you can trust slowly get the car up to the speed where it makes the noise and see if you can pinpoint it. If not check for anything that is hanging that could scoop up air or rattle when air hits it.
I had a MB truck that used to ping because the driveshaft didn't have any cardboard in it.[IMG][/IMG]

 

not a fuel pump sound?

 

I have this same problem with my 2002 C200.
The noise seems to be more to engine rpm rather than speed.
It is loudest at around 2000 rpm whatever is the speed.
The local dealerships I visited claim that it is normal engine noise, not related to transmission.
Shan.

 

Does it have a turbo ?? maybe a leak during high boost

 

Ok I did the following test. At the speed where I hear the whining/singing noise, I shifted to neutral. The sound stayed excactly the same.

What does this exclude: diff, tansmission, anything else.

Any other ideas.

it definately does not have a turbo

 

Its just a thought, are you running any kind of heavy tread winter tires?

In my Jeep ZJ (Grand Cherry) heavy feet make a huge difference and certain speeds.

I think I'd rotate the wheels and get the wheel/axle bearings checked.

My C320 2001 has done 115k Miles and is as quiet as a mouse!

Good Hunting.
PB

 

Good news. I know the problem.

My uncle's 190 had the same problem. It turned out the gears inside the rear differential were singing. They were worn out because the lubrication inside that crown dried out.

So now, i guess MBs tend to have this problem after 100K miles.