The Stovebolt Site Forums The Shop Area The HiPo Shop Sticking Disc Brakes

Hi Guys,
My truck is so close to being done I am itching to get it out!

I have a problem with my disc brakes. I have a camaro rear end with discs and the aftermarket front disc kit on the original straight axle.
The master cylinder is from a 4wheel disc corvette (77-82).

When I drive, the truck seems fine at first, but the more I press the brakes the more they stay on and heat up.
Only the front ones stick.
When I get back to the shop I jack the truck up and can hardly turn the wheel, only when I crack the bleeder am I able to push the piston back so it spins (fairly) freely.

The master cylinder is new (hooked up front to front and rear to rear). The calipers are all new (two years ago). The hoses are new, the lines are new, and the fluid is new. I thought I must have the wrong master cylinder and that it has a residual value in it, but I verified with Napa this morning that it is a 4wheel disc m/c. I have an adjustable proportioning value on the rear brakes, nothing in the front.
There is play in the linkage between the m/c and my pedal. I have also bled the brakes twice yesterday to make sure there is no air or debris in the lines.
Because the calipers work fine when the bleeder opens would this mean that the problem is before them?

I checked again with Napa, that m/c is from a power system. I believe the 69-76 can be had in non-power. Could anyone verify that this would cause the problems I am seeing?

Thanks!

You've got slack/play in the pushrod, that's good.

My first guess is a flexible line collapsing and acting like a check valve, I know you said they are new, but new is not always perfect.
Does this happen to both front brakes, or only one? If both then my line theory is less likely and you're back to the MC as the primary culprit. Disassemble it to see and or exchange it.
Present your troubleshooting method to NAPA, if it seems logical and points to the new MC then ask what they have to offer.

Grigg

Thanks for the reply Grigg,
It is happening to both front brakes fairly equally.
The guy at Napa said that it seemed likely that it was the m/c. I have ordered the earlier corvette manual m/c. I guess I will try it and see. I'm not sure what else it could be...

Here's my take on your problem. I've seen this problem several times. The rod between the M/C and booster is too long. You need to adjust the rod with the ball exiting the booster. Just behind the ball you should find a nut which, when locked down, keeps the output rod or shaft from getting longer or shorter. That shaft is threadrd so you can make it longer or shorter. There is a special tool for this adjustment (cost less than ten bucks). The tool looks like a "H" with a rod through the center section. There should be about 0.020" gap between the booster rod and the M/C rod.

He claims there is play in the linkage between MC and pedal ...
Could add a little more just to double check.

Thanks for the replies beltfed and Grigg,

I got the master cylinder from the older corvette, where the rod goes in is much deeper. I put it on and set up the rod a little bit different. Bled the brakes and went for a nice long drive and they never got hot at all.
So I don't know if it was the linkage or the m/c but either way it works and I am cruising!
Thanks for the help!

So for future people searching this thread. If you want manual four wheel disc brakes, use the 68-76 Corvette Master cylinder.

Even with the rod misadjusted/to long, there still can be play in the pedal. The classic example of this problem is...vehecle with cold brakes drives fine. then after several miles the brakes pads heat up and it will not coast. It drives like your E-brake is on.

After I posted, I noticed he had changed the M/C to one with a deep socket. Deep socket M/C's are most ofter used in drum/drum setups. They have the small reservoirs. Disc brakes require the large reseroirs due to several things. I would warn Colin to check the fluid in the M/C often. Reason being as the disc pads wear the fluid level is gonna drop.

I had the same problem with both front disks sticking. Everything was new and tried adjusting the rod did not work , put a corvett master on and my breaks work great.