HEY FOLKS, I NEED SOME SERIOUS HELP WITH THE BRAKES ON MY 76. I HAVE CHANGED ALL FOUR ROTORS, ALL FOUR CALIPERS ALL FOUR BRAKE LINES, THE PROPORTIONAL VALVE AND THE MASTER CYL. 6 TIMES. AFTER I BLEED THE BRAKES THEY WORK FINE FOR ONE DAY AND THEN THE PEDAL GOES TO THE FLOOR, THE WARNING LIGHT COMES ON AND THE CAR DOESN'T WANT TO STOP. IT HAS BEEN TO THE CHEVY DEALER AND TO TWO BRAKE SHOPS AND NOONE CAN FIGURE OUT WHAT IS WRONG.

I HAVE BEEN TOLD THAT THE CALIPERS ON THE REAR OF CORVETTES CAN SUCK AIR BUT THIS DOESN'T MAKE ANY SINCE TO ME. IT WOULD SEEM TO ME THAT IF IT CAN SUCK AIR IT WOULD ALSO LEAK . THE SYSTEM HAS BEEN CHECKED AND ALL FITTING ARE TIGHT AND THERE ARE NO LEAKS ANYWHERE. THE MASTER CYL. IS ALWAYS FULL WHEN YOU TAKE OFF THE TOP.

I REALLY NEED HELP WITH THIS PROBLEM.

What sequence were the lines bled? I had a similar problem after replacing the right front brake line and flushing all of the lines. Turns out I hadn't bleed them in the correct order.

In the Chilton's Corvette 1963-82 Repair Manual (#28500) I have page 9-9 says the correct sequence for vehicles with four wheel disc brakes is: left rear inner, left rear outer, right rear inner, right rear outer, left front, and right front. (Haynes Repair Manual for '68 through '82 lists the same sequence)

Since doing the bleeding in that sequence the brake pedal has stayed rock solid, even over the winter while in storage. Hope that's all it is to correct the problem for you.

Your assumption that the calipers would leak if they could suck air is incorrect. The sucking is caused by rotor runout. If you are sure the bleeding is correct, I would check the rotors.

I would also check to make sure you aren't leaking fom anywhere. It might sound stupid but make sure the shoes are installed correctly in the calipers, you might have a set of shoes that the backing plates were warped.
Do you have a power booster on the master cylinder?

I replaced my leaky calipers with "Stainless Steel Brakes Corporation" Calipers. I used their manual to install and bleed the system. Their suggestions on bleeding the calipers is:
Pedal Bleeding.
This requires two people- one to pump the brake pedal, and another to operate the bleeder valves. After each bleeder valve is opened individually, the assisstant should depress the brake pedal one full stroke. The valve operater observes the fluid for air bubbles and closes the bleeder valve before signaling the assistant to slowly return to the released position.
Note: In order to assure that no air can be sucked back into the system, a plastic tub should be connected to the bleeder valve. The other end of the tube should run to a partially filled jar of brake fluid and the end of the tube submerged at all times during the bleeding process. In addition, the bleeder valve must be closed at the end of each stroke, before the pedal is released.
Continue in this manner until one or all calipers are bled.
Refill the master cylinder after each caliper has been bled and check the reservior of the system system being bled, frequently.
Bleed the longest line first, in this order: right-rear outer, right-rear inner, left rear outer, left-rear inner, right front, left front.

I used this proceedure when I did my brakes, and I haven't had any trouble at all. I did this two years ago.

It scares the heck out of me to think that the brakes might give out at any time. I sure hope that it never happens to me. That would be an early heart attack!!!

E-mail me if you have a problem.
blk79

|UPDATED|5/16/2002 7:59:57 PM|/UPDATED|

I also have info on the pressure differential switch.

Recentering pressure differential switch.
If the warning light will not extinguish:
After bleeding is completed, turn ignition switch to the "on" position. Have an assistant depress the brake pedal slowly to build up pressure. While pressure is being held, slowly loosen the nut at the outlet port of the pressure differential switch opposite from the side of the brake system that was bled last. As soon as the light goes out, tighten the nut securely.

blk79

http://www.bmw-m.net/TechProc/bleeder.htm

Click on this www. for a cheap pressure bleeder.

|UPDATED|5/21/2002 7:35:51 PM|/UPDATED|

Let me jump in here and tell you about my experience this weekend in dealing with my brake problems. I have had everything replaced on my entire brake system and I mean everything. My frustration level was to the point that I was considering selling my vette, just like so many other shark owners I could never get a good pedal and the warning light on the dash could not be extinguished short of removing the bulb. After two and a half years of taking my vette to no less then 10 mechanics and spending close to 4 grand and after bleeding the system 40+ times all I have is an expensive braking system that wouldn’t work. I HAVE HAD ENOUGH. I took matters into my own hands and have read countless posts from hundreds of shark owners with this problem, including this post from Bill Meador, who describes exactly what I have been putting up with for 2 ½ years. I also bought all the repair manuals I could find for my 75 and educated myself on vette maintenance. I systematically ruled out all possibilities for my particular brake problem and surmised that the bleeding process was the root of my brake dilemma. I will spare you on all the details that led up to this diagnosis and just get to the bottom line. NORSKY IS RIGHT ON THE MONEY.
GRAVITY BLEEDING IS THE MOST EFFECTIVE WAY TO BLEED YOUR BRAKES IF YOU FOLLOW THIS SEQUENCE. YOU WILL GET FAVORABLE RESULTS. If you read the GM Manual it goes into detail as to why you have to follow this sequence. I bled my own brakes this weekend and then took it on a 100 mile cruise subjecting my brakes to numerous hard stops and although there was a slight degree of brake fade due to the system heating up, The dash warning light is out and I am confident it will remain that way for a long time.
As the old saying goes, If you want something done right, you have to do it yourself.

GOOD LUCK BILL MEADOR.



|UPDATED|5/19/2002 8:19:25 PM|/UPDATED|

Joe, glad to hear you were able to get your brakes solid again.


Jim O.

OK Joe !

Glad to hear you got them fixed. I guess there are a lot of different ways to fix things, and evidently yours is one of them.. Did you have to raise the rear of the car about a foot higher than the front in order to make it work? Maybe a stupid question.... My method sure fixed mine.. Maybe the miles on the car makes a difference. Bearing runout, etc.etc... I only have 13300 miles on mine. My calipers just rusted from not being driven. Replacing with SS calipers did the job...