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MB Paul
MB Paul, Mercedes Technician
Category: Mercedes
Satisfied Customers: 4317
Experience:  Mercedes Benz Qualified Diagnostic Technician
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I have a 2006 56 E280 petrol. There is a whine from the engine

Customer Question

I have a 2006 '56 E280 petrol. There is a whine from the engine which is engine-speed related, so it's not the gearbox.

I have had the drive belt guide pulleys replaced, but that has had no effect. I suspect alternator or water pump bearings, but would welcome a professional opinion and advice about how to eliminate this.
Many thanks,
Robert Knight
Submitted: 4 years ago.
Category: Mercedes
Expert:  MB Paul replied 4 years ago.

MB Paul :

Hi Robert, noises can be tricky to identify and in the first instance I would remove the V belt to see if the noise does go away when running the engine breifly with the belt removed.

MB Paul :

The idler or tensioner pulleys are the most common problems so at least you have eliminated these

MB Paul :

We also see problems with the alternator, water pump or the AC compressor - with the idler pulleys you can usually feel if these are worn by spinning them by hand, the other drives are usually less obvious but do try spinning each in turn to see if any feel rough when spinning them

MB Paul :

If the noise has gone with the belt removed and you cannot identify which one is at fault by hand then the belt will need to be refitted and I would next recommend using an automotive stethoscope to help pinpoint the noise. These are fairly inexpensive and although I prefer a good quality electronic one the standard cheaper versions can be very helpful in tracing noises

MB Paul :

Here are a selection of these: Automotive Stethoscopes

MB Paul :

Trying to pinpoint the noise without one of these is very difficult - a long screwdriver to the ear pressed against each drive in turn or a long piece of vacuum tube in the ear can also be usefull but a correct stethoscope is really the best tool to use for identifying noises

MB Paul :

Best regards, Paul