2nd Gen Non-Engine/Transmission Brake pedal goes to floor after bleeding

[SMalafy]

I just had done a complete brake job on my 95. Rebuilt calipers, new pads, new brake lines and new rotors and also changed the rear shoes. I bled the brakes and the pedal was hard but as soon as I started the truck up the pedal goes to the floor. I changed the booster and the master cylinder last year and did not have this problem before I did the brakes over again. I have no loss of fluid from the master cylinder so what else could be bad ? Is it the proportioning valve ? When I did the brakes both calipers were seized.

 

[GAmes]

I would double check every wheel for a leak. The brake fluid has to be going somewhere.

 

[BigPapa]

Sounds like you may have blown a rusted out brake line. Most of the time it's the one along the frame behind the fuel tank. The fluid has to be going somewhere. Find the leak and you'll find your problem.

 

[jelag]

You don't have the calipers on the wrong side with the bleeder valves on the bottom of the caliper instead of the top.... if you've switched them and the bleeders are on the bottom... you can't get all the air out of the system... and the pedal will be soft.... BTW when you purchase off the shelf calipers... make sure you have a pair.. its not uncommon for someone to screw up and put (2) lefts, or rights in the same box..

 

[SMalafy]

Calipers are on the right side with screw facing up

 

[SMalafy]

Replaced all brake lines with copper/zinc lines last year.

 

[SMalafy]

No fluid leaking anywhere !

 

[petersonj]

It is possible that the rear brakes are way out of adjustment, or some rear brake hardware is out of position, or even a rear wheel cylinder cup flipped when replacing the brake shoes. If a wheel cylinder cup is the culprit, it may take awhile for the brake fluid to become visible.

- John

 

[SMalafy]

I will pull the drums but I do not notice fluid level going down in the MC

 

[BigPapa]

If there's no fluid leaking then I'd say your MC is bad.

 

[JR]

If you have rear ABS you may have air in the system if you allowed all the brake fluid to drain out of the master. If the truck has good enough brakes to safely get to a dirt road try doing several panic stops. Get the wheels to lock up and cycle the ABS. Then go back home and bleed the brakes again. Only other option I'm aware of to bleed the ABS is through DRB software.

 

[mwilson]

If you have rear ABS you may have air in the system if you allowed all the brake fluid to drain out of the master. If the truck has good enough brakes to safely get to a dirt road try doing several panic stops. Get the wheels to lock up and cycle the ABS. Then go back home and bleed the brakes again. Only other option I'm aware of to bleed the ABS is through DRB software.

This ^^^^^^^^^^^^

Sounds like you still have a gob of air in there somewhere. If you let it go completely dry you may even have to bleed the master cylinder.

 

[SMalafy]

Thanks. I am waiting for the weather to warm up and I think I have some brakes now to work with. If I do I will take it to a shop that has the DRB.as I already questioned them about this. Its hard trying to bleed brakes by yourself.

 

[JR]

Its hard trying to bleed brakes by yourself.

That is exactly why I bought a pressure bleeder. They are a little pricey but do the job well. Pneumatic vacuum bleeders are also the cat's meow.

 

[SMalafy]

I bought one of those years ago but the cover that goes on top of the MC did not fit well and I wound up sending it back because I could not get it to work right.

 

[phantomusa]

If your pedal slowly goes to the floor your master cylinder is bad
Pappy

 

[tugboat1st]

I had to put clamps on the cover of the pressure bleeder to get it to seal. Then it worked good.

 

[tugboat1st]

I have a similar problem with my peddle going down. It pumps up and gradually goes down with steady pressure on the peddle. No fluid anywhere. I have replaced the master cylinder three times, 2 rebuilts and 1 new. Same thing. Adjusted rear brakes twice. Peddle came up but still bleeds down.

 

[phantomusa]

It's simple you either have fuild bypassing or a leak my best guess is your master is bypassing fuild
But that's a dangerous situation you need to find the cause of your pedal dropping

 

[tugboat1st]

If that be the case then three master cylinders have all had the same problem and one of them was brand new. And there have been no leaks detected and no fluid loss.