68 Rear Brakes
Thread Starter
6th Gear
Joined: Jul 2012
Posts: 6
Likes: 0
68 Rear Brakes
I just purchased a 68 corvette. It came out of storage from the owner's barn, where it had been in storage for years. The back brakes don't work. not weak, they don't work at all. We've fixed all the leaks in the line, and bled the brakes over and over. Anyone know why the back brakes dont work?
Thanks for your time.
Thanks for your time.
Thread Starter
6th Gear
Joined: Jul 2012
Posts: 6
Likes: 0
That was our thought too. We took out the brake serts on both sides in the back, and it pumped out the fluid when we hit the brakes. The whole stream of brake fluid. Also, you can drive it around, and the front brakes still work perfectly. Does that sound like a master cylinder problem?
Melting Slicks
Joined: Feb 2006
Posts: 2,092
Likes: 5
From: Fayetteville Arkansas
how does your pedal feel? Is it weak/soft? To test the master I'd take vise grips and clamp off the soft hoses just before the rear calipers. That should produce a hard pedal if the master is good or no air is in the line somewhere before the rear calipers. Was the master empty or run dry at any point? Diagnose the problem before you start buying and replacing parts that you may or may not need.
Sully
Sully
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Melting Slicks
Joined: Sep 2004
Posts: 2,655
Likes: 19
The switch that turns on the light works off differential pressure between the front and rear system. If you're sure you got all the air out of the master cylinder and calipers, it's the master cylinder seal. But if your master cylinder was dry, it can be difficult to get the air out. It's usyally reccomended to bench bleed. But if you're going to remove it, you might as well replace a potentially bad 40 year old part that's under $20.
Melting Slicks
Joined: Feb 2006
Posts: 2,092
Likes: 5
From: Fayetteville Arkansas
If the master was run dry you probably still have air in it. Go to Napa or Autozone and get a bleeder kit for like $10. Disconnect the hard line and hook up the plastic bleeder kit then run the hoses back up into the master. Then start pumping the pedal until all you see is fluid coming out with no bubbling. Quickly reconnect the hard lines and then rebleed the entire system. This time start at the front driver's, then front passenger, then rear driver's inner then outer, then rear passenger inner then outer as the service manual instructs. I know everyone has said do the bleeding farthest to closest but the service manual from GM has it the other way. And don't forget the rear caliper have two bleeders. One for each half and both should be on top of the caliper halves.
Sully
Sully
Team Owner
Joined: Jun 2000
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From: Southbound
Cruise-In II Veteran
Purchase the chassis service manual and follow the directions for bleeding Corvette brakes. After sitting all that time, you should expect to find the master cylinder and all four calipers need to be rebuilt - at the least - or replaced (better all around).
Instructor
Joined: Nov 2006
Posts: 130
Likes: 1
From: Wylie TX
I finished a complete brake install yesterday (new master and all 4 calipers). Bleeding the brake system (following the service manual instructions) takes some time.
Bleeding the rear brakes took three times as long as the fronts. There is a lot of line to get the air out for a proper bleed. Also, there is less fluid in the rear reservoir (at least on my 69) and you will need to check that level often.
Also, I just noticed your comment about upper and lower bleeders. There are two bleeders on each rear caliper, but they are "inside and outside", both on the top. The inside one is hidden and barely visible unless you stick your head in the wheel well. Make sure you have bled that one too.
Bleeding the rear brakes took three times as long as the fronts. There is a lot of line to get the air out for a proper bleed. Also, there is less fluid in the rear reservoir (at least on my 69) and you will need to check that level often.
Also, I just noticed your comment about upper and lower bleeders. There are two bleeders on each rear caliper, but they are "inside and outside", both on the top. The inside one is hidden and barely visible unless you stick your head in the wheel well. Make sure you have bled that one too.