Brake Bleeding Question, Weird Problem

[fierrogt]

Hey guys,
I have a '67 camaro that I just put Touring Classics C5-Hybrid front brakes and '00 Camaro rear discs. I have everything run and I gravity bled the system, then did the two-man method (Until I saw no bubbles in bleeder line). With the car off I have a firm pedal, as soon as the car starts in gets soft. The rear brakes can barely stop the wheels from turning on jack stands and pedal goes to the floor. Here are the things I have already done/checked:

-Bench-bled Master Cylinder
-Checked for Visual Leaks
-MC full of fluid
-Tapped calipers as I bled

I am not sure where to go from here. Could it be air trapped in the MC, and I need to bench bleed again? Thanks for the help

Forgot to add- It is a power booster setup and I am running the long pushrod.

[vintageracer]

Does the "red" brake light in the dash come on when you hit the brakes? Is the brake pressure switch light/wire even hooked up at the distribution block? Are your brakes power assisted?

You may have the brake bias switch slammed to one side in the distribution block eliminating the pressure to the rear brakes. This can happen when installing a new front brake system during the brake bleeding process. If the brake bias light is hooked up and it is red when you hit the brakes that can be your problem as to why you have no rear brakes. You may need to re-bleed the system with the car running if it has power brakes and re-center the bias valve in the distribution block. If this is the problem, re-center the bias valve by slowly re-bleeding the front brakes with the car running (power Brakes). Pump up the brakes as you would normally when bleeding. The red brake light will probably be on and slowly bleed the front calipers watching for the brake light to go OUT. The instant the brake light is no longer lite (goes out), close the bleeder and do the other caliper. This will re-center the bias valve. You can then re-bleed the rear brakes starting at the right rear, left rear, right front, left front. In extreme cases where the distribution/bias valve is old and cruddy, you may have to disassemble the valve, clean it and re-center the bias valve.

I assume that you are also running the correct 4 wheel "disc" brake master cylinder for the long push rod. What type of proportioning valve are you running? Is the proportioning valve in the distribution block (combination valve) or a separate proportioning valve in the rear brake line? If the proportioning valve is separate and in the rear line, do you have the valve turning to full lock the wrong way? This would also limit fluid pressure to the rear brakes.

I will be that the bias valve is slammed to one side in the distribution block. Try that first!

[fierrogt]

Thanks for the response. I am running a power booster, with dial style proportioning valve in rear line (from summit) but no distibution block, just a T into the two front lines. I think I have figured out the problem (after bleeding the system 4 times!) I had a rebuilt caliper on the rear passenger side, and after talking to Noel at Touring Classics, I determined that the caliper was bad (pretty sure the piston seal was leaking). Going to the parts store tomorrow to pick up a new one. I hope this works, i need a car to drive!

[k9ulan]

im curious if this solvedyoutr problem

[fierrogt]

So I just spent the last 3 weeks trying to finish my brakes with no success. Replaced a caliper and rebled the system a thousand times no air in it, but no pedal and the brakes BARELY worked. I finally gave up due to time constraints and the fact that it is my only car and took it to a mechanic. Somehow the front right brakeline had a piece of plastic clogging the line partially. But there was enough pressure for it to bleed (sort of). Anyway, plastic gone and the brakes work great. Just thought it might give somebody else fighting their brakes something to check.

[zz3elcamino]

I am confused....Hpw did the piece of plastic in the right front line keep the rear brakes from working properly? I am asking because I may be running into the same problem. My front brakes feel good and make good contact with the rotors, but the rears calipers don't make contact with the pads until the pedal is pressed. Thanks