Well In did some checking and it only happens after driving a couple miles. Pads heat up and expand causing them to grab. It is only the rears. I drove it again today just to see. To start off with in "N" I can push the car myself with no problem. Within a half mile I start to notice the grabbing and coming back home gets really bad. Rear end is squatting and takes more gas pedal to move. I backed the car into the garage to lift the rear and going backwards was even worse. Got the car up in the air and in "N" I could not physically move either rear wheel. Took the wheels off and cracked the bleeder on I think the pass. side and free'd the rotors. So could this be from "run out"? I know both rear rotors have been replaced b/c the rivets are gone. But why now? Could it be b/c I never had all the air out of the rears before? This is killing me!

 

from reading this post I know what I would have to do if your car came into my shop. I would first check all what you have done to make sure the master cylinder and stuff is all correct. ( not saying you did it wrong..But I have to make sure it is right)....I would install my brake fluid pressure gauge that can measure your brake fluid pressure at the rear calipers and I press the pedal and see what the gauge shows and then see if it goes back to zero.

I would also suspect the rear rubber brake hoses due to not reading that if they were changed or not. They can fail and create a check valve internally in them due to split or crack in the inner hose....thus...holding brake fluid pressure and not allowing to the release.

I do not feel it is on your master cylinder staying engaged due to the front brakes engage before the rears do...so...knowing that it is only effecting your rear brakes. I think it may be a hose issue...but I do not know if both wheels are locked up or not.

DUB

 

Thanks DUB for your reply! I think it may be coming from the left rear because as soon as I opened the bleeder for that caliper I was able to turn the rotor and since it has limited slip it turned the other side as well. So that tells me maybe the culprit is in that caliper. I'm looking for a brake pressure gauge now so we'll see what happens.

Yes the fronts are fine. The hoses were replaced last summer when I first installed the calipers with braided stainless.

What doesn't make sense is what's holding the pressure?

 

I think I might have found something. You can see that the rotor in not spaced equally in the caliper. Looks like it's touching the caliper itself and the pistons are out about a 1/4 " on the outer edge and in on the inboard. I'm sure this is not normal but how is this corrected? This is the drivers side. Pass. side is a little better. Also I turn the rotor by hand with effort in forward direction but can't turn them in reverse.

 

MC diaphram could be going bad

 

sticking pins. very common on brakes. get new pins lube them up really well prior to installing. brake grit gets in and they gummy up and don't release as easily as they should.

 

These are new calipers?? Where are the pins?

 

The 'pins' are what hold the pads to the caliper. Technically...only one 'pin' per caliper.

I can say it does not have to do with 'sticky pins'. The pins are not going to cause the caliper not to be centered. Nor causing for pressure to stay in the system.

NOW..I can CLEARLY see the caliper and the rotor Look at the parting line in your rear caliper where the two halves come together.. See how it does not line up with the casting line in the center of your rotor cooling fins as you show in the first photo of POST#24?

Now go look at your front calipers and see if the parting lines match up.

Either you will need to use a washer to space the caliper out...or your caliper mounting bracket is cracked and leaning towards the caliper.

I do not see how this is causing the pressure to stay. I would get it to lock up again and then release the brake fitting on the other side and see if it does the same thing or if oyu certain it is the caliper that you tried this on first.

AND...not meaning to make you think I am stupid for asking this...but are you sure the Willwood master cylinder is made so the lines that attach to it are like they would be on your era of Corvette....because....the photo below shows how they can be installed backwards...due to how the master cylinder is designed.




Because IF the master cylinder is designed like the one in the photo above...then it is actually your FRONT line is not releasing...even though it is going to the rear...and thus...the master cylinder may not be correctly adjusted if there was some specific dynamic Willwood requires.


DUB

 

The m/c I have is like the original the rear reservoir and outlet is for the rears and connected properly but excellent point.

I did add a washer to center the rotor and looks right on now but spoke with Wilwood again today and he told me if they are grabbing and when you open the bleeder and fluid comes out. Then the booster rod is too long as many of you have suggested. So I cut an 1/8th" off the booster rod and reassembled. Now at work and ran out of time for the bleed sequence. I'm praying this is it!!

 

Well I think I got it saying that loosely.. No more dragging but the brakes feel no different than when I first started I guess. Maybe better but wouldn't be much. I can't get the rears to lock up?? Should they with the fronts? When I get my pressure gauge I will compare the pressure. from the front to the rears although I was told the rears will be less. Thank you everyone for the comments and suggestions.

AL

 

I do know the rear have to be able to grab and hold. When I have the rear of the car up in the air and the rear wheels are turning. I can press the brake pedal and get the wheels to stop turning....and this is done when teh engine is IDLING and in gear.

I would not say that I would want them to lock up...so-to-speak....but when I did apply the brake pedal in a 'panic stop' scenario..I would want then to grab and stop turning. from what I was told by a good friend at Master Power Brakes...the pressure in a panic stop will be quite high but then being to drop off...if I understood what he was saying when we talked about the pressure reading I should be seeing when I test different systems.

DUB