Need Help
Thread Starter
Junior Member
Joined: Mar 2005
Posts: 10
Likes: 0
From: partlow virginia
Car: 87 iroc z
Engine: 350 tpi
Transmission: 700r4
Need Help
WHEN I HIT THE BRAKES IN THE CAR IT SOUNDS LIKE AIR BLOWING LOUD AND IT MAKES THE ENGINE IDLE DOWN TO WHERE IT WANTS TO DIE. I HAVE CHANGED THE BRAKES AND IT DOESNT HELP WHAT COULD IT BE
TGO Supporter
Joined: Jul 2003
Posts: 4,803
Likes: 2
From: Grand Rapids, MI
Car: Z28
Engine: Sb2.2 406
Transmission: Jerico 4 speed
Axle/Gears: Ford 9" 3.60
Sounds like a major vacuum leak in the booster or affiliated vacuum system. Have you tried replacing the hose between the intake and the booster? If not, may be time to replace the booster.
Vacuum testing the booster would be ideal, if replacing the hose and check valve proves to be unsuccessfull.
"Aside from that, you are correct in the being able to press the brake twice before the internal pressure is equalized. Run the engine for a short bit, allow full vacuum to generate then shut it off and test it. Another thing to try after you do that is, while the booster is in the depleted state, start the engine with pressure on the pedal. When started, the pedal should drop slightly. The double pedal push tests for leaks in the system, the latter tests the plunger for operation."
That's from another thread where I gave help on trouble shooting a booster.
Vacuum testing the booster would be ideal, if replacing the hose and check valve proves to be unsuccessfull.
"Aside from that, you are correct in the being able to press the brake twice before the internal pressure is equalized. Run the engine for a short bit, allow full vacuum to generate then shut it off and test it. Another thing to try after you do that is, while the booster is in the depleted state, start the engine with pressure on the pedal. When started, the pedal should drop slightly. The double pedal push tests for leaks in the system, the latter tests the plunger for operation."
That's from another thread where I gave help on trouble shooting a booster.
Member
Joined: Jun 2000
Posts: 180
Likes: 0
From: Manassas, VA, USA
Definitely sounds like a vacuum leak, and probably it is internal in the booster (need a new booster). The booster normally has vacuum on both sides of a diaphram, then when you push the pedal it should close the vacuum valve to the back side and open an air valve so that you get air pressure on the back side helping push on the master cylinder.
Sounds like it is not closing the vacuum valve, so that you are basically just opening a massive vacuum leak whenever you push the brake pedal.
A way to test it would be: disconnect and plug the vacuum line to the booster. Pump the pedal a bunch until there is no more power assist. Now drive it a bit (in a SAFE AREA since you'll have no power assist) and see if it still makes the noise when you hit the brakes. If not, it is definitely related to the vacuum booster (which is replacable seperately from the master cylinder, meaning you don't have to mess with bleeding fluid or anything).
Sounds like it is not closing the vacuum valve, so that you are basically just opening a massive vacuum leak whenever you push the brake pedal.
A way to test it would be: disconnect and plug the vacuum line to the booster. Pump the pedal a bunch until there is no more power assist. Now drive it a bit (in a SAFE AREA since you'll have no power assist) and see if it still makes the noise when you hit the brakes. If not, it is definitely related to the vacuum booster (which is replacable seperately from the master cylinder, meaning you don't have to mess with bleeding fluid or anything).