77 Brakes
Thread Starter
Cruising
Joined: Jun 2006
Posts: 10
Likes: 0
From: Lampasas Texas
77 Brakes
Hey ya'll thanks for the welcome and here is my first question... I was having a little fun on HWY 190 and finally had to use the brakes when to my unpleasent surprise the pedal went softly to the floor and the brake light came on so I replaced the mastercylinder (bench bled)changed all the pads with ceramic pads (did I screw up?) bled the system and I still have weak pedal ~!@#$%^&*... The rotors appear to be fairly new and true and I did not notice any leaks at the calipers, any tricks or advice out there would be appreciated
Drifting
Joined: Jan 2006
Posts: 1,944
Likes: 22
From: Yooperville MI
You probably still have air in the system. It could be caused by not bleeding enough or you might have too much run-out in a rotor causing air to be sucked in which usually happens only in hard braking situations. With standard caliper seals, you are only allowed .005 run-out on the rotors, you really can't feel that in the pedal.
Double check the calipers again (now that it has sat) for leaks around the pistons and the bleeders. I'm sure you checked the master cylinder fittings for leaks. If you are bleeding with the pedal, you may need to go around the car 2 or 3 times. The factory bleed procedure on Vette's is different than conventional cars. And the Vette procedure differs among different publications (GM, Chiltons, etc). GM manuals suggest that you start at the nearest wheel to the master, not the furthest. Chiltons suggests starting at the left rear, etc. Even if you do it in a different sequence, it will work, but it will take longer.
Double check the calipers again (now that it has sat) for leaks around the pistons and the bleeders. I'm sure you checked the master cylinder fittings for leaks. If you are bleeding with the pedal, you may need to go around the car 2 or 3 times. The factory bleed procedure on Vette's is different than conventional cars. And the Vette procedure differs among different publications (GM, Chiltons, etc). GM manuals suggest that you start at the nearest wheel to the master, not the furthest. Chiltons suggests starting at the left rear, etc. Even if you do it in a different sequence, it will work, but it will take longer.
Race Director
Joined: Sep 2004
Posts: 11,874
Likes: 263
From: Arlington Va Current ride 04 vert, previous vettes: 69 vert, 77 resto mod
these cars are pain to bleed the air out of them.....for $60 you can buy a motive pressure bleeder and enjoy life or you can hase this bleeding beast for a while....also check the rubber lines and see if when some pushes on the brake they bulge...i usually put like almost a quart through the system when i bleed my brakes...
Melting Slicks
Joined: Jan 2004
Posts: 2,672
Likes: 1
From: New Cumberland PA
I guess I am one of the lucky ones. I replaced most items and had the complete system drained. Filled it up and bleed the brakes with a helper, my daughter. In my opinion the most important thing is to purge the air. Opening a bleeder until fluid comes out is not correct. It is imperative to make sure the fluid does not contain any air. The best way to do it if to attach a clear hose to the bleeder and watch the fluid. Once the fliud comes out you'll see air bubbles in it. Keep bleeding until the fluid is clear of all bubbles. My brakes may take more brake effort than today's cars but I have a hard pedal that grabs about 1/3 of the way down. I can lock up the brakes if I want to. Since I also changed rotors, I made sure run out was within spec. I started at .016" run out and got it down to the .005 range. Most garages have no idea on how to work on full floating piston calipers.
