really hard brake pedal
Thread Starter
Drifting
Joined: Dec 2007
Posts: 1,672
Likes: 8
From: Sumter South Carolina
really hard brake pedal
'89 FX3 - feels like my brake booster isn't doing it's job and the car is still relatively new to me so I'm just getting to the brakes. Breaks feel normal until I have to apply anything over 15% brake power, then they stiffen up. I read that I might need to just engage the anti-lock but once it rained I slammed the brakes but they just locked up. There is not anti-lock warning light so I'm thinking the brake booster is fine but something with the anti-lock is messed up. Maybe past owner tampering?
Any ideas of where to look would be appreciated...
Any ideas of where to look would be appreciated...
Le Mans Master
Joined: Jan 2003
Posts: 5,858
Likes: 7
From: Santa Maria CA
You should be hearing the ABS pump prime (spinning sound) upon each startup when you reach 4 MPH coming from behind the driver's seat in the rear cargo area. This is an ABS system self check.
If you happen to have your foot on the brake pedal during this priming you will feel the pedal pulsate. This is what you would feel when the ABS is kicking on in a real situation also. You can also brake from about 5-10mph on loose gravel to make the ABS kick in.
On my '86 if all the ABS harness connectors are unplugged inside the ABS compartment the ABS light on the dash will never illuminate no matter what. Are you hearing the ABS pump cycle? Any hissing from the brake booster?
The ABS system was designed as a passive system meaning that if it where to fail inoperative your normal braking would remain fully functional and unaffected.
If you happen to have your foot on the brake pedal during this priming you will feel the pedal pulsate. This is what you would feel when the ABS is kicking on in a real situation also. You can also brake from about 5-10mph on loose gravel to make the ABS kick in.
On my '86 if all the ABS harness connectors are unplugged inside the ABS compartment the ABS light on the dash will never illuminate no matter what. Are you hearing the ABS pump cycle? Any hissing from the brake booster?
The ABS system was designed as a passive system meaning that if it where to fail inoperative your normal braking would remain fully functional and unaffected.
Last edited by 86PACER; Nov 14, 2010 at 01:57 AM.
Safety Car
Joined: Jan 2004
Posts: 3,759
Likes: 8
Generally, when you have hard brake pedal. Then it is the booster. A booster can fail at any time, and you can usually hear it hissing. Or it can fail over a period of time where you still have brakes, but the pedal is real firm. Then you put in a new booster and have easier brakes.
Burning Brakes
Joined: Jan 2003
Posts: 755
Likes: 32
From: Roswell Georgia
Check The Brake Booster First
Just finished replacing the brake booster in my '89. I experienced sudden failure (hard brake pedal) at an auto-x. Brakes still worked, but required extreme pedal pressure to stop/slow down. Got the Vette home, did all the normal checks on the vacuum check valve, vacuum line, etc. Everything checked out okay; but no power brakes. (I didn't hear a hiss when slowly pressing down on the brake pedal with the engine off so the booster itself seemed normal.) Used my Kent-Moore tool to cycle/test the ABS system with no effect.
Decided to go ahead and remove the master cylinder to see if it was leaking (bad seals maybe). As soon as I removed the master cylinder from the front of the booster, I found the problem. A 3" split in the plastic front cover of the booster in the area hidden by the vacuum hose from the plastic storage tank and electrical wire spiral wrap on the side of the booster next to the engine. Ended up replacing the booster assembly and the problem was resolved. (Had to remove the driver's seat and some of the lower surround to get to the two nuts holding the rear of the booster to the firewall, but other than that, no problem!)
Good luck fixing the problem.
Decided to go ahead and remove the master cylinder to see if it was leaking (bad seals maybe). As soon as I removed the master cylinder from the front of the booster, I found the problem. A 3" split in the plastic front cover of the booster in the area hidden by the vacuum hose from the plastic storage tank and electrical wire spiral wrap on the side of the booster next to the engine. Ended up replacing the booster assembly and the problem was resolved. (Had to remove the driver's seat and some of the lower surround to get to the two nuts holding the rear of the booster to the firewall, but other than that, no problem!)
Good luck fixing the problem.
