Brake pedal hiss

C.D.

I changed my rear pads today, but it is quite possible that this problem existed beforehand but I never noticed as I never used the brakes as described below. Car is an 07 Volvo C30.

When the car is idling and is stationary, there is a hiss from the brake pedal when pressed. Once the pedal has traveled a certain distance, it stops. If the pedal is pumped in that particular range, the hissing will occur which each press.

When the car is off, there is no hiss and the pedal firms up as expected. When driving there is no hiss and good brake response.

There is no evidence of a leak on the calipers and no traces of leaked fluid around the Servo. Fluid level is constant.

Research suggests it is the brake servo, though in those cases it happens while the car is in motion. It is supposed to be a €1,000+ job at Volvo and what with the nature of my work I do not have a good indie I would trust (I travel a lot). Can anyone shed some light on this? If it is the servo, is it urgent? My understanding of its operation is that if there is a Servo leak, worst case scenario is I will not get vacuum assisted braking, but will still have braking.

Captain Slow IRL

If it is a hissing noise, it could very well be a leak in the servo. It won't stop you braking but it will make braking very difficult if you lose all servo assistance.

Is the hissing noise only while the pedal is moving or can you hold it steady at a certain point (or range of travel) and still hear it?

C.D.

Only when the pedal is moving, if held at a particular point there is no hissing or "hardening" or "softening" of the pedal. I will get my housemate to help me find the exact location of the leak.

Would you recommend waiting to see if brake performance decreases over time before getting it fixed, or is it likely to fail catastrophically? At the moment, brake performance is spot on.

Captain Slow IRL

If there was a gradual decrease over time, you probably wouldn't notice the lack of assistance getting worse. It would be a lot wiser to get it sorted now rather than risk an accident.

It might be no harm to ring your local volvo dealership, this may be a common occurence with a simple fix.

C.D.

Update in case any fellow boardsie has the same problem. Took it to a main stealer last week (few bits and bobs to be done) and was told it is perfectly normal.