My brake light stays on and the brake pedal gets "squishy." There are no leaks anywhere to be found and the fluid in the master cylinder doesn't decrease even after a lot of driving.

I've bled the brakes (not full bleeds though) a couple of times but it keeps happening.

Could the master cylinder be putting air bubbles into the brake lines? I am stumped on this one.

Any help would be greatly appreciated.

Matt

 

Are you getting air when you bleed the brakes? If not I would try a new master cylinder.

 

I am getting air when bleeding them. But there's no leaks anywhere. That's why I was thinking it was the master cyl somehow putting air in the lines.

Matt

 

You probably have excessive rotor runout, and are pumping air back into the system via the seals in the caliper pistons. It's a very common problem with Corvette disc brakes, especially if the rotors have been replaced. When the car was assembled, the rotors were riveted to the hubs/spindles. This was then "trued" as a unit to remove runout. Once you replace the rotors, or have a warped rotor, it wobbles, and pumps air. The wheel bearing could also have excessive wear, causing the rotors to wobble. Check them with a dial indicator. I "THINK" that the max runout should be in the range of .003...that's 3 thousandth's. Hope this helps. Check the archives. This topic has been beaten to death. Chuck

 

Will this involve replacing rotors if there's runout? If so, any recommendations? Vette Brakes and Parts?

Matt

 

You don't necessarily have to replace the rotors, there may be enough material to have them turned true.

However, before you go to that trouble, I'd bleed the hell out of your brakes. Vette brakes can be very finicky about giving you good pedal. Gravity bleed, then two-person bleed, and while you're bleeding, have someone tap lightly on the caliper that you're working on with a screwdriver handle or something similar to free up any bubbles hanging on the inside walls of the caliper. Also make sure you're bleeding the calipers in the right order (you're repair manual, Chiltons or whatever, will tell you the right order).

THEN you have to reset the brake warning light. I believe you do that (if I remember right) by stepping on the brake very hard once. But you may want to check the manual to be sure. Otherwise the light will never go out.

Also, you may be seeing air when you bleed that's not coming from the brake lines--I drove myself crazy for a while when I first bled the brakes on my '78 getting bubbles all the time, until I realized (someone here suggested it) that I was getting air around the threads of the bleeding nipple. I never did stop getting bubbles, but my pedal is high and hard now.

JB

'78SA


[Modified by JB, 6:24 PM 1/15/2002]

 

Do you have new calipers? I had the same problem and it was the calipers that were bad. I had no fluid leaks but air would get into the system. I had restored the car and replaced every single part of the brake system except for the front calipers, they were relativly new. The brakes worked great for a couple of years . New front calipers and now I have great brakes.

 

SOUNDS LIKE YOUR MASTER CYLINDER IS BYPASSING I WOULD REPLACE IT FIRST SOUNDS JUST LIKE THE SAME PROBLEM I HAD ON MINE ......I REPLACED IT AND IT FIXED THE PROBLEM .... YOU MAY WANNA CHECK YOUR BRAKE HOSES TO THE COULD HAVE CRACKS IN THEM MINE DID SO I REPLACED ALL OF THIS ON MINE AND I NO LONGER HAVE THE SQUISHY BRAKE PEDAL I WOULD RECOMMEND REPLACING THE BRAKE HOSES WITH STEEL BRAIDED BRAKE HOSES WELL WORTH THE MONEY AND THEY LOOK COOL TOO !!!!!! :cheers: :cheers:

 

I have to agree with Chuck here. With your car being an 80 it is only fair to assume that the rotors have been cut at least once but more then likely more then that. If they are at the point where they can no longer be cut the likely hood of runout or warpage increases. If they have even a sligh warp in them every time the high spot on the rotor goes past the caliper pistons that will cause them to cavitate in their cylinders causing the air in the lines. Also look down into the caliper from the top, between the pads and the pistons, what do you see, is there a lot if crud build up there? That could be 2 things, 1- road dirt sticking to the leaking brake fluid (actually creating somewhat of a seal) or 2- the rubber from the o-rings breaking up. Both can be where your air is coming from.

I had the same trouble with mine. I wound up going to Muskegon Brake and getting the entire kit. Kit included: 4 SS calipers, rear SS lines, front rubber lines, all clips, new master, 2 qt dot 5 fluid. To that I added 4 new rotors, front inner and outer bearings with seals, all new lug studs and nuts. After core rebate everything was $640. Well worth it I thought.
Good Luck
JoeB