W202 Hissing Sound

[BIG J]

Hi all,

Got a problem with my C-Class from the driver side right air vent I get a hissing sound when it's in park or my foot on the brake (Auto) only time it's not there is when I have my foot down on the gas.

Any Ideas?

Cheers

Amarjit

 

[0ptic]

Not sure if this could be anything to do with it but have you popped the bonnet and listened under there? The break servo (vacuum operated) is in that area of the engine bay. leaking pipe or servo unit?

 

[pingping]

Not sure if this could be anything to do with it but have you popped the bonnet and listened under there? The break servo (vacuum operated) is in that area of the engine bay. leaking pipe or servo unit?

yep sounds like a pipe got a hole in it or similar

 

[Pac]

Might also be the vacuum pipe between turbo and intercooler? I had this split on my w203 which resulted in the same sound.

 

[BlackC55]

Check the headlamp vac pipes. They are most common.

Move the headlamp adjuster dial to "3" and see if it goes away. Also check if the headlamps move correctly.

 

[BIG J]

Thanks all.

If it is the servo is there anyway to test it as want to 100% sure it is that, I can test the servo on my mustang by pressing the brake then starting the car and if it drops slightly it's fine, will a star machine tell if it's faulty?

Cheers

Amarjit