Strange buzzing from behind dash

[hafez]

Not sure if this would be considered Engine or Electronics but - My uncle has a 01 C-Class Merc and recently there has been a strange buzzing from somewhere behind the dash/under the bonnet. It only happens when you are going at about 25mph+ and dissapears when the steering wheel is turned to the left.As you accelerate, the pitch of the buzz also goes up. He has asked a few mechanics but they don't seem to have a clue. Anyone have any idea?

 

[Ian B Walker]

If it was a 124 or a 201 I would say its an air leak from the headlight adjuster.

 

[Harley Man]

Hafez, what model is it? if its a C220 or C270 Cdi you may have a small split in one of the turbo hoses, I had this on the one I had, and it was a pain to find

 

[grenachenoir]

That sounds like a similar sound on my W124 coupe - Ian, where do I find the headlighht adjuster?
Adam

 

[Ian B Walker]

That sounds like a similar sound on my W124 coupe - Ian, where do I find the headlighht adjuster?
Adam

Right hand side of the steering wheel next to the light switch is a dial / knob that you turn to either raise or lower your lights depending on what load you have in the boot. Its Vac controlled and buzzes when it is disconnected. HTH

 

[hafez]

It's a C180 if it helps

 

[grenachenoir]

Found it. Stops buzzing when set above zero. Where do I start to look for leaks?

 

[Ian B Walker]

Found it. Stops buzzing when set above zero. Where do I start to look for leaks?

Pull off the light switch, then undo the nut (22mm), carefully remove the plastic trim and then pull out the offending switch. There are two or three vac lines going to it dependant on what car you have. These have rubber sleeves on them. Check for cracks and splits. If non then renew the switch (£23 approx from dealers)