I own a '02 Volvo S60 T5. A few days ago I noticed a hissing sound coming from the brake pedal area near the floor board. This hissing sound is constant when the car is running. When I turn off the car the hissing sound continues for a few seconds then dissipates. When I press the brake pedal the hissing sound diminishes and if I press the brake pedal down all the way the hissing sound disappears altogether. Obviously air is escaping from something.

I crawled underneath the steering column with a flashlight to see if I could spot the problem. I had the car running while I did this. Here's what I noticed (please forgive me for not knowing the technical terms for any parts I try to describe).

The brake pedal is connected to a black brake arm. About half way up this arm there is a gold rod/bar that extends from the brake pedal arm through the floor board (at least it looks that way). Along this gold rod/bar there is a rubber sleeve that looks like the bellows (folds) of an accordion. It seems like the hissing air is coming from this part. However, as I used my hand to feel all around the sleeve, I felt no escaping air. I depressed the brake pedal several times and watched this part in action and again, the hissing would diminish or disappear completely depending on how hard I depressed the brake pedal.

I don't know what's on the other side of the floor board where this gold rod/bar seems to extend through. Though I got under the hood, then jacked the car up and got under there to look, I was unable to see where the rod/bar came out of the floor board.

Any ideas what could be happening?

 

sounds like the vacuum booster has a leak.

r.

 

Reg,

Thanks for the response. Is the vacuum booster the rubber sleeve I'm talking about?

 

That rubber diaphragm is the cruise control servo if I am not mistaken. At least the older models had this rubber thingy. I can be bought at the dealer if this is what you are referring to. Can you take a pic and post it?

 

Pics attached. Kind of awkward to get a good pic, but hopefully this will be what you need.

 

Your brake booster is the large circular 'can' on the engine side of the firewall. The brake master cylinder is bolted to it.

r.

 

So is the part I posted pictures of on this thread the cruise control server? Is the brake master cylinder also on the engine side of the firewall?

 

The part is on the firewall. The big round thing bolted behind where you put in the fluid. It is leaking through the boot. That is not the servo as I suspected that was only the older models.


So basically, you need a new brake booster.

 

+1 to the brake booster.