brake booster?
Thread Starter
2nd Gear
Joined: Jun 2010
Posts: 2
Likes: 0
brake booster?
Hey on my 76 vette im having a brake problem. there is vacuum going to the booster and iv bleed the brakes. the pedal feels great with the engine off, but as soon as i start it my foot basically hits the floor. there arnt any leaks that i know of and i bought a new master that iv bench bled. the booster's pushrod does work and there is strong vacuum so im not sure whats going on. iv heard that on vette power brake systems the engine needs to be running, is this true?
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
Boosters seldom fail, but get falsely blamed for all kinds of brake ills. In order to correctly bleed one of your calipers, the broken bleeder will have to be removed.
If you do not have a good quality set of flare nut wrenches, my advice is not to try any further brake work without them.
If you do not have a good quality set of flare nut wrenches, my advice is not to try any further brake work without them.
Team Owner
Joined: Jul 1999
Posts: 65,492
Likes: 230
From: Orange Park Florida
If you want to actually fix your brakes so they feel great, ensure a feeling of confidence when applied, unlike any other vacuum assisted car, and want 100% total reliability....do the following....
rebuild your hopefully already Stainless lined calipers with O rings pistons and toss the backing springs...new pads, check rotors to see if there is not much wobble as they rotate between the pads...less than 1/32 inch side/side is fine, any more and it could be troubles..
ditch that 'proportioning valve' really just a brake light switch...put in a front splitter just like in rear....
and finally do a Hydroboost conversion, run off the power steering pump and ditch that silly vacuum booster....remember one thing...vacuum sux....
well worth the effort....the final results will amaze you....
rebuild your hopefully already Stainless lined calipers with O rings pistons and toss the backing springs...new pads, check rotors to see if there is not much wobble as they rotate between the pads...less than 1/32 inch side/side is fine, any more and it could be troubles..
ditch that 'proportioning valve' really just a brake light switch...put in a front splitter just like in rear....
and finally do a Hydroboost conversion, run off the power steering pump and ditch that silly vacuum booster....remember one thing...vacuum sux....
well worth the effort....the final results will amaze you....
Melting Slicks
Joined: Mar 2007
Posts: 2,520
Likes: 11
From: Hinckley OH
Since you have a broken bleeder screw, I doubt you were able to successfully bleed that caliper. You will need to either replace the entire caliper or take the caliper off and attempt to remove and replace the bleeder screw. I have never been able to successfully get a broken bleeder out, but it has always happened on one of my daily drivers and I didn't have a lot of time to work on it so I just bought a caliper.
Drifting
Joined: Feb 2005
Posts: 1,788
Likes: 131
I have the same problem on my 75. New master bench bled, all four corners vacuum bled. With the engine off the pedal is hard 1/2" from the top. Hold your foot on the brake, start the engine and the pedal will go 80% to the floor. I rebled everything twice. The fluid level never changes so I know I don't have a leak. The next step was to buy a booster but that doesn't fit the woes of the problem I'm having.
If a calliper was leaking air wouldn't there be a fluid leak also ?
If a calliper was leaking air wouldn't there be a fluid leak also ?
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Race Director
Joined: Feb 2006
Posts: 12,239
Likes: 19
From: Chino CA
I have the same problem on my 75. New master bench bled, all four corners vacuum bled. With the engine off the pedal is hard 1/2" from the top. Hold your foot on the brake, start the engine and the pedal will go 80% to the floor. I rebled everything twice. The fluid level never changes so I know I don't have a leak. The next step was to buy a booster but that doesn't fit the woes of the problem I'm having.
If a calliper was leaking air wouldn't there be a fluid leak also ?
If a calliper was leaking air wouldn't there be a fluid leak also ?
Drifting
Joined: Feb 2005
Posts: 1,788
Likes: 131
Pulled the front calipers off.... the seals look really bad and the pad is soaked. I'm getting 4 new calipers and pads. Alot cheaper than a crash. I haven't driven this car in the past two years and it is probably my fault. I'm also forgoeing the 1 year warranty stuff for lifetime. Don't want to fall down that steps again. Convertible season is so short. I hope the parts get here quickly.
