Brake Problems - Any input appreciated

Great job. Thanks for the update! You might consider using a 2 lb residual valve as the 10lb valve may cause the rear brakes to drag and wear out prematurely. It would be an easy replacement as you have already got it plumbed. Again a great job!!.

 

BobMcD,
Thanks, your posts were particularly helpful.
Jon

 

Does your master cylinder sit level on the firewall? If not level the car so MC sits level and bleed. Used to do that witha lot of older GM's. Air gets trappped in the MC. If your lines go above the MC, bleed there first. I know your bleeder scwews are on the top, right. Hope this helps

 

Agreed -- 2# for disc, 10# for drums.
And regarding post 13 -- it does not matter where your MC is mounted, you should use residual valves in any case.

Glad you solved the problem !!

 

great info---good work

 

When using the newer small GM calipers with parking brakes is the same true that the parking brakes need to be applied when bleeding?

I am haveing trouble with these as well.

 

Not covered here, if the master is on the firewall, it'll gravity bleed very nicely, a little patience is in order. Open the bleeders, wait till fluid comes, no pumping, just let nature do its job. Believe it, it does work.

 

A little backround on residual pressure check valves. Originally they were used with drum brakes and built into the master cylinder. Their purpose was to prevent air being sucked into the brake system past the wheel cylinder cups when you lift your foot off the brake pedal . With the advent of disc brakes, residual pressure was no longer needed or wanted as the excess pressure can cause disc brake calipers to drag and cause the pads to wear out prematurely. When we start designing our own brake systems and have a low mounted master cylinder is where we have the need for some residual pressure check valves to prevent air from being drawn back into the system when you lift your foot off the pedal. As has been stated 10 psi for drums and 2 psi for discs. With a high mounted master cylinder, and 4 wheel disc brakes, residual pressure should not be needed. But in Jon's case with these particular type rear calipers the piston seems to back off a little more than most when you lift off the brake pedal. That's where the 2lb valve to the rear only helps to maintain a good brake pedal. If you are using a disc brake master cylinder with drum brakes, there is no check valve in the master cylinder. That's when you would want to use a 10Lb residual check valve, regardless of where the master is located. . It would be put inline to the drum brakes only. With a high mounted master front disc brakes don't really need any residual pressure as gravity takes care of that.

 

Yup....
When I finished the brakes in my avatar, I didn't get back to it for a week or so....
was surprised to find the brakes had bled themselves -- topped off the fluid, nice strong pedal !!

 

Try this:
Start car. Hold brake pedal down. With the brake pedal held down, operate the parking brake several times. It should ratchet back to give you decent pedal height. It's supposed to ratchet back by itself when you use the parking brake alone but doesn't when the pad retracts the ratchet doesn't engage. Holding pads down with the brake pedal keeps the pad snug to the rotor and the ratchet will eventually work when you operate the parking brake several times. You can release the parking brake by either shifting out of park or using the manual release under the dash. It's difficult to find but it's there. Use this technique when the pads eventually wear and you want to raise pedal height again. No disassembly is required.