Question about Cars & Trucks
My Buick is making a hissing noise under dash when I push the brake pedal. I have to push SUPER hard to get it to stop. It's sucking at the brake pedal plunger under the dash, going into the firewall (when I push the pedal/when it makes the hissing noise). I run the vehicle for a minute and turn it off and crack open the 90 degree fitting coming out of the brake booster and it sucks in there too. ???
Sounds like a possible air pocket in the braking system. Do you know how the bleed the brakes? They may need to be bled. Also, if you've added brake fluid recently, and didn't put the cap back on, it could create a suction. Another note is to check the cap to the brake fluid reservoir. It's rare, but, it could be bad.
Posted on Jul 10, 2013
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Posted on Jan 02, 2017
SOURCE: Bad Brakes
I would be looking at the ABS valve. one way to test the booster is to start the vehicle while you ae depressing the brake pedal, you should feel the brake pedal drop a little bit, this is a sign that the boostr is working properely. you may want to check to see if there is any air in your system as well.
hope that this helps.
Posted on Oct 16, 2008
It maybe, I don`t know the vehicle personally but on Trucks and Buses, when this occurs, it usually points to the master cylinder piston seals which moves in and out as the foot pedal is operated. Does the hiss alter as the pedal is pushed down?? Does the hiss reduce or increase as the pedal is pushed down?? If it does, I think you`ll find that it`s this air seal between the piston and cylinder that`s failing and not the servo. Whether you car works the same way, I don`t know but I presume it must. Ian
Posted on Aug 06, 2009
The brake booster has a ruptured diaphragm. Replace the booster.
It is located under the hood between the brake master cylinder and the firewall.
Your master cylinder may be leaking fluid internally past the plunger.
Have it examined when you change the booster.
Posted on Oct 12, 2009
you mean you hear air in the cab down by the pedal. If thats the case your power steering assist is leaking. Its the big black unit behind the brake master cylinder. It may set a check engine light at times for lean condition.
Posted on Nov 19, 2009
most likely have a bad diaphram in the brake booster that hisssing sound is vacuum leaking under hood there will be hose going to brake booster unhook hose and pinch off hose start car does hissing sound disappear if so bad booster
Posted on Sep 03, 2010
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