The Stovebolt Site Forums The Shop Area Driveline New brake install, pedal goes to floor

I have installed the Hollister Road front disc kit on my 53 1-ton, as well as their 1.25" bore master cylinder with the Wilwood proportioning valve. I also installed a 10-lb residual valve to the original rear drums. I bled each wheel twice after I got a steady stream of fluid at each wheel. All wheels have strong fluid flow when you push the pedal. You can hear the rear drums working.

Do not have a pedal at all, it goes to the floor.

When I push the pedal, the rear drums do stop the back wheels from spinning, but the pedal is on the floor. The front discs do not do anything unless I pump the pedal 8-10 times and then the front discs will stop the fronts from spinning. The pedal is still on the floor but you can feel some pressure. But as soon as I let off the pedal and push it again I have no fronts and no feel of pressure until I pump 8-10 times again. While I am rapidly pumping the pedal it feels like it is trying to build pressure but the pedal will go to the floor when I hold it.

The new master cylinder is in the stock location under the floor, but has a remote reservoir on the firewall. 1/4" brake lines all around.

My original stock master cylinder and front drums had done the same thing but not as bad, I could pump them 3 times and have a hard pedal. This new setup, no pedal.

Is there trapped air that won't bleed?

Do I need residual valves on the front?

I have never had this happen.

Thanks in advance for any wisdom.

Are the rear brake shoes adjusted correctly.............nice and tight........dragging on the drums both shoes both sides ???

Hy Chad M, if the master cylinder is mounted below the level of the disc brake calipers, then 2 p.s.i. residual pressure valves are recommended to prevent backflow to the master cylinder from the calipers. That being said I don't believe that is causing your lack of pedal. I don't mean to insult you, but in trying to think where air could be trapped the only thing I could think of is could the calipers be upside down with the bleed screws facing down rather than up? I would be tempted to remove the brake lines from the master cylinder and plug the ports to make sure the master cylinder is not bypassing. Did you bench bleed the master cylinder?

"Hy Chad M, if the master cylinder is mounted below the level of the disc brake calipers, then 2 p.s.i. residual pressure valves are recommended to prevent backflow to the master cylinder from the calipers."

3B,

I recently converted the otherwise original brake system on my '36 Chevy pickup to a tandem master cylinder. The OEM '36 master cylinder has a 15 psi residual pressure valve in it even though the master cylinder is above the level of the wheel cylinders. The factory would not have done that if it were not required. In doing my tandem conversion I put a 10 psi Wilwood residual pressure valve in both the front and rear brake circuits to try to approximate what the factory did in 1936.

Based on what I found in my '36, I would say that Chad needs a 2 psi valve in the front circuit in addition to whatever else his problem is.

Thanks for the replies.

I did not bench bleed because of the remote reservoir, but I did gravity bleed per the instructions. I might power bleed next.

The front calipers have the bleeders facing up.

I will double check the rear drum adjustment.

I think if all this fails I may plug off the the master cylinder and see if its not bad.

I agree that Chad probably needs a 2 psi RPV up front and that he should check the rear shoe adjustment again.. If the replacement master cylinder does not have an integral RPV for the rear brakes, which it probably doesn't, then A 10 lb RPV would be correct for rear drums.

Also, if the new master cylinder has a proportioning valve, then it has to have the brake warning switch removed and a dummy plug installed in the proportioning valve to keep the valve from moving during brake bleeding. The plug is generally sold separately, which is always annoying.

Honestly though, I would first look at the master to see if it was bench bled properly prior to being installed.... The nice thing about these trucks is that you can use a jack to level the master, so you don't need to remove it if you need to bleed it again.

Update...

Step 1 - tightened up the rear shoes. No difference.

Step 2 - bled the master cylinder, minor improvement.

Step 3- bled the fittings on the proportioning valve, no change.

Step 4 - got a pretty good vacuum bleeding kit and bled everything twice again with that, no change

Step 5 - adjusted the pushrod on the pedal/master. That seemed to help a tiny bit.

I have a slight pedal now, and it gets better if I pump it 10 times but it bleeds off when I release and push it again.

Continuing to diagnose...

You can tell whether the problem is in the front or rear by pumping up the pedal & removing the MC cover. You will see the fluid flowing back into the reservoir & that will tell which section has the problem. You may need a helper for this.

First you don't need residual valves.
The front lines should be 3/16", drum lines are 1/4"

The rod between the booster and master most likely needs adjustment. It should be about 0.020" from the master cylinder indent. This will bring up the pedal engagement

The easiest way to do this under the truck is separate the master off the booster and adjust the booster pin nut out 1 turns and then slide the master back on, It it sit flush the bring it out another turn, repeat until it does not fit flush and the turn back in one turn. This is often easier on the bench but doable under the truck rather quickly.

http://repairguide.autozone.com/zne.../80/09/2a/86/medium/0900c15280092a86.gif
this is a picture of the nut adjustment. The tool you don't need just the pliers and a 9mm ( i think ) wrench

Also turn the prop valve adjusting knob so its about mid way between all the way up and all the way down then rebleed the back.

The pedal will never be as high and and firm as it was with drums and no booster, The feel more resembles a modern pedal where its never really rock hard except when its off and no vacuum.
It seems low when your static engine off and not moving but when you are running and vacuum is applied it starts stopping with far less effort than before. Your pedal should be firm about 4" from the floor, engine off and not moving. Once it's moving and running you will see that it starts to stop at a higher pedal than 4" , this is due to the booster assist, if you adjust the rods to tight then you end up with your nose on the steering wheel every time you attempt to stop.

You can call me up to 9 pm CST to help you get it set up any day of the week. If I don't pick up leave a message with a good time to call back and i'll call you as soon as I can

This is any easy fix so don't make yourself crazy with it.

Thanks Dave, I will dig into it tomorrow evening or Friday and if I get stuck I will call you.

ok

Well I adjusted some more with just very slight improvement, and bled and bled some more. I had just enough pedal to keep it off the floor so I took your advice and drove it into the driveway. It stops very well but its by far the spongiest brake pedal I have ever felt. So its back on the road! Much thanks, Dave and everyone else.

Planning a brake upgrade this winter.............A few questions:

The truck stops but the pedal is low or is spongy or is spongy and low ?

Does the pedal height or stoping power change if the pedal is pumped ?

Well I think the problem all along was my anticipation that I would have a pedal feel that is "normal". This setup from Dave @ Hollister performs very well at stopping the truck, but the pedal feel will deceive you at first. When you push the pedal, the brakes start engaging very early and gradually. Its like you have a very wide range of braking pressure due to the long pedal travel in our trucks. It is not touchy at all, if you want to slow 5 mph you just push the pedal about 1.5"! If you need to stop hard you can do that too. Its way different than anything I've ever experienced.

Thank you also to HotrodLincoln Jerry for telling me how to set up a vacuum canister, and everyone with feedback.

Glad you got it sorted out. The pedal feel is very different due to the leverage you get from that long brake arm.