There is a hissing sound coming near the rear tires. It's on both sides. The hissing sound cuts in and out. Anyone else have this problem with their 05 C230k.

 

my 03 has this same hissing. my assumption would be that is is exhaust related. 18K miles later and nothing has happened here

 

Did you change your wheels? I have noticed that many non-stock wheels using new bolts seem to either 1) Have the bolt be too long and you'd hear a clicking sound or 2) The bolt is just BARELY too long and you will hear a whish whish sound that comes and goes.

 

Could you tell me more about this clicking sound? I have this annoying click when driving at low speed over small bumps and the dealer cannot seem to find it. The recently installed the new 05 Sport Rims on my car too.


Thanks,
Bill

 

It's not so much of a clicking sound. It's more like a leak kind of noise. Sounds like its releasing some pressure or something. I'll take it to the dealer anyways and see what they say.

 

It is the fuel pump! Even my 1986 does that, you hear the fuel pump which on the W201 was under the drivers side rear passenger seat. Not sure where it is on the W203 as I have never looked for it. Also not sure if the W203 has dual pumps or a single unit either. But the sound is probably a mixture of exhaust flow sound and fuel pump! The exhaust will drown out the fuel pump sound once in a while so you do not hear it constantly.

 

Is this probably why cuts in and out. Also, I only hear it when the car is on. I assume if there was a leak, I would hear the noise after turning it off.

 

Yes, the hissing sound is from the electric fuel pump. It is located in the rear of the car, right around the rear wheels. This is a common noise and explains why you only hear it when the car is turned on!!

 

fuel pump aye? that explains it. I thought it was a nail in my tire at first then i incorrectly assumed it was the exhaust since its the drivers rear tire side.