I have a 1994 C180 with an obvious vacuum leak. When accelerating, the centre air vent closes and all air comes from the side vents until the throttle is released. </P>


Vaccum is fine at idle, sufficient to retract the rear headrests.</P>


Trying to track the leak down, but workshop manuals seem to omit any form of vacuum circuitry (I reckon it's as important as the electrics!).</P>


Does the C class have a vacuum tank behind the front left hand road wheel, like my previous Benzes? I'm guessing some kind of non-return valve has failed or there's a leak in the tank.</P>


Thanks,</P>


Robert</P>

 

Hi,
My 94 C180 has exactly the same problem as yours. However it is even worse. The centre air vent closes even at idle. I can hear an air pump at the back keeps running for more than 5 mins after startup of ther engine. The rear headrests won't work at all. I have no idea what is wrong. According to your description, it seems to be a vacuum leakage somewhere, could you give me some more hints so I can track the problem? Moreover, is it possible related to electric problem such as relay failure? I have little experience on the vacuum tank but it seems Mercedes cars have many vacuum control parts. Thanks.

Albert

 

both of you: your vacuum is motor driven and no need for the vacuum tank.

yes it is a leak. pull out the rear seat and check where it is leaking.

keeping the vacuum pump running all the time will wear out the carbon brush on the armature and it is not separately sold. you need to buy the whole central locking pump!

 

Hi there,
I'm a newbie here.Just happened to read this post while browsing and I thought a little opinion might help (hopefully).

I had this problem just recently on my 95 C180. I found that a vacuum hose under the hood was hanging loose (green). Yes, it was a vacuum leak. There is a vacuum distributor/manifold/whatever-name-you-may-call-it under the hood, on the right hand side (from driving position), close to the firewall, that supplies vacuum to the center air ducts. It's got its vacuum source from the intake manifold.

Hope this helps.

Bob

 

broken vacuum elements often leaks too.