I'am having brake problems on my L-46 vette. In the last year and a half
I have installed 3 master cylinders and am still haing the same problem.
I get a mushy brake pedal after a month of driving. there are absolutly no leaks anywhere. I put it up on a lift checked all brake lines, pulled the
calipers off and checked all the pistons for leakage. The calipers were replaced around ten yrs ago with stainless steel lined cylinder bores. Thanks in advance.
Shaun :cheers: :cheers:

 

http://forums.corvetteforum.com/zero...519331#1519331

Check out this thread.
Oh, welcome to the forum. :cheers:

 

I am assuming that you have completely eliminated the M/C as a cause- "new" or rebuilt master cylinders may sit on a shelf for so long that they are rusty internally, right out of the box. I disassemble & check all master cylinders before I install them. You would be amazed at how many I have had to return.

Presuming no leaks as you said, the fact that your brakes start out okay and then gradually fade is a sign that your rotors have excessive runout.

If it were hoses, it would start out not-ok, not fade gradually.

Excessive runout causes the rotors to pulse the pistons which causes them to pump air into the caliper, behind the piston. This is because the Vette calipers are designed to maintain constant contact between the pads and the pistons. Some people remove the springs to counteract this. Zero tolerance pistons & seals will help, but it has been suggested that they also fail over time. They work so well, that the owner ignores the runout, and the pulsing rotors cause the zero tolerance pistons to slap against and egg-shape the caliper bores. Then you have to replace the calipers as well. The best solution is probably to true up your rotors (or replace them with new, straight rotors), and then install the zero tolerance kits. I, personally don't use the ZT kits because I'd rather maintain my rotors properly, and use stainless pistons which will not corrode in the outer seal area where most leakage problems begin.

Also, don't assume that new rotors are straight right out of the box. I just bought a new set and they were way off.

 

Welcome to the nightmare of Corvette brakes! I had all 4 calipers redone, 4 new rubber lines, rotors trued (while on the car) and a rebuilt master cylinder. $1100 AUS and the pedal is still mushy. :mad

I was driving down the highway on Sunday and my brakes "pumped up" so hard that I only had to touch the pedal to activate the brake. Once I slowed the braked locked on but went back to normal after I pulled off the road. :confused:

Further down I had to brake suddenly, but this time the pedal went to the floor! :eek: :eek: 2 pumps, 3 pumps so it was time to compression lock it. 3rd to 1st doesn't do much for the gearbox, but it's better than a front end rebuild!

Found the left front caliper had leaked some fluid. rebuilt 18 mths ago with ss sleeves. :mad

Throw the stock ones in the trash and buy some zero tolerance ones or the ones with the lifetime warranty.

 

I had the same problem. It turned out to be a warped rotor.