Contour Enthusiasts Group Archives Forums General Troubleshooting Brakes make hissing noise!!! What the heck?!?!

Ok, this is actually a problem with my new Focus ZX3 but I still totally identify with these boards and trust you guys above everyone else!

So here it is...if I depress my brakes to a certain point they make this loud hissing sound!! It sounds like if you were depressurizing or putting air into your tire! A hissing noise!!!

And it's just at this one point! If i depress the brakes further the sound goes away. If I release the brakes the sounds goes away! But if i leave my foot just on that point it makes a very loud hissing noise!

What is that?!?!?!

Where does the noise seem to be coming from? If it seems to be coming from the brake pedal area, or slightly to the front of the pedal, you may be hearing the power brake booster. Some vacuum noise from the booster is normal. Does the engine run a bit rough when you hear the noise? If not, there is probably not a vacuum leak. If the booster is leaking, you will need to replace it.

Are you losing fluid from the reservoir? If so, it could be a leaking slave cylinder. I had the same hissing sound on a former car and the rear cylinder was scarred.

The sound definately seems to originate from around the brake pedal itself. The engine does not run rough when i hear the hissing noise.

In fact, the engine doesn't have to be on at all. Nor does the car have to be moving. I can just hop in my parked car, depress the brake to that certain point and I get the continuous hissing noise until I move off that point.

Will check resevoir to see if I'm losing fluid in the morning!

Thanks for the help, guys!!!!

Brake booster vac....

dang it...i was hoping maybe that's just the way it's supposed to be...

i have to take it to the dealership now, don't i? ugh...i hate taking the car in. how involved will it be to fix this?

oh well...

Thanks Terry!!!!