Hissing sound from steering wheel area

mercedes-benz
m-class

#1

Hi. My 2002 MBZ 320ML just started having a hissing noise from what appears to be under the steering wheel. It goes off when I put on the brakes, or when I am traveling on the freeway above 30 mph. Should I be scared?


#2

Yes, this is a potential problem, as it is almost definitely a leak in the power brake booster, or in the hose leading to the booster.

If booster fails completely, you will still have brakes, but the amount of force that you will have to use on the brake pedal could be a problem unless you have very strong leg muscles. I would suggest that you get the car to a reputable independent mechanic (NOT Midas, Meineke, Monro, Sears, Pep Boys, AAMCO, or any other chain operation) a.s.a.p.


#3

I am not that conversant with 2002 MBZ technology. But, the hissing could well be a leaking power brake booster if Mercedes uses that on your vehicle. If it is now leaking it would be letting excess air into the intake manifold which could affect the engine control system. If this leak is truely from the the brake booster, the problem could get worse.

Drop the car by the Mercedes service department and have them hear the hiss and advise you. Hope this helps.


#4

Thanks. My husband is not very helpful on things like this, though he fancies himself a car afficionado.

Do you have ANY idea what that could cost?


#5

If the repair requires a genuine Mercedes part, it could be quite expensive–potentially a few hundred $$, I would guess. However, whenever brakes are a problem, you really have no options but to get the problem repaired.

As the old says goes, there is no such thing as a cheap Mercedes.


#6

yes, that is true…though for the first 100,000 miles, it was on the house, so to speak, part of their maintenence plan (and extended warranty). They quoted me $900 for the part alone, but given the economy, they will look at it for ‘free’, and then give me the bad news, I suspect. The hiss has been driving me nuts, and I cannot be in a car that will crash. It does have almost 150K miles on it. :slight_smile: