Engine squealing

[Gee82]

The engine in my C280 Sport has developed a squealing noise from the front of the engine that increases with engine revs, it idles silently!

The noise doesn't sound like a belt it's more like a mechanical squeal from something.

Any suggestions?

 

[kid-jensen]

Water Pump?

 

[Gee82]

I suppose it could be but the water pump was only replaced in June this year!

 

[hexflyer]

I've just had the same noise on my C250turbodiesel used to go quiet when warm but is now constant, a squeal coming the water pump viscous fan area, so looks like the pump is on the way out, no leaks yet though

 

[television]

The best way to pinpoint the item is to use a long large scewdriver as a stethoscope. By putting the blade end on things like water pump,alternator,etc and the handle to your ear, you will hear the component that squeels.

Do take care of any fans in the near.

Malcolm

 

[jberks]

As Malcolm says, get a screwdriver and trace the noise. It could also be the alternator bearings or for that matter anything on the belt. As you've had the water pump replaced, it's probably not that. The one occasion I've changed a water pump (my C220), it rattled rather than squealed anyway. It was replaced at 4 years and has been fine for the last 7 so they aren't a frequent failure.

 

[dava]

Fan belt tensioner.

 

[Parrot of Doom]

Try removing the belt, and turning each pully by hand to feel for worn/failed bearings.

 

[Andy Wr]

Auxillary belt tensioner, on my C180 it was ok while in N or P but as soon as a gear was engaged thus putting load on the tensioner it used to emitt an high pitched squeal. Easy diy job to replace.

 

[dava]

Spray the tensioner with WD40 while runnig TAKE CARE not to catch hands!!!! and see if it changes the noise, it's quite a common fault for these to fail/make a noise.

 

[Parrot of Doom]

I wouldn't spray WD40 onto a belt - belt dressing spray is much better.

 

[JohnnyW]

What's belt dressing spray, and where can you get it? My C200 is squealing like a pig at the minute!!!

 

[oigle]

If you are only looking to isolate the noise, spray the belt with a soapy water solution. No point in buying special stuff for such a job. If the noise goes away, then look at getting whatever is needed to rectify the problem.

 

[Hibbo]

What's belt dressing spray, and where can you get it? My C200 is squealing like a pig at the minute!!!

A good trick is to cover the belt with soap. Try and jam a bar of saop against a pulley and let the belt do the rest!

It will stop the squeal, but you may end up with an engine bay looking like the aftermath of a bukkake party!

 

[Gee82]

Using a process of elimination and using a drive belt diagram I found on this forum it seems that it is my Alternator pulley which is making the squealing noise!

Can I just buy a new pulley rather than a full new alternator?

I have no other problems with the alternator regarding charging its just the noise its making.

 

[Gee82]

Can anyone answer this?

 

[Hibbo]

It is highly unlikely that it is a faulty alternator/alternator pulley that's causing the squeak, it's just that the belt isn't tight enough and is slipping on the alternator pulley as that's the one with the most load on it. Does the squeak stop if you lever the belt tensioner to pull the belt tighter?

 

[dava]

Yep you can just change the pulley, it's a reconised fault on MB. It has a clutch system inside and held on with a allen key bolt, modern MB vehicles realise when you asking for full power from the engine via the ecu and allow the aircon pump and alty to idle, ie disegage the pulley/clutch, thus ensuring you get the full BHP from the engine and no loss to the auxilary units. However, you'll probably fine it wont just pull off. Need a proper puller and even then it may not come off.

 

[Hibbo]

Yep you can just change the pulley, it's a reconised fault on MB. It has a clutch system inside and held on with a allen key bolt, modern MB vehicles realise when you asking for full power from the engine via the ecu and allow the aircon pump and alty to idle, ie disegage the pulley/clutch, thus ensuring you get the full BHP from the engine and no loss to the auxilary units. However, you'll probably fine it wont just pull off. Need a proper puller and even then it may not come off.

Well I stand well and truely corrected!

I'll stick to only talking about vehicles over 15 years old!