braking problems

[Dillon79scotts]

I recently replaced my 1/2 running gear for 3/4 ton. bled the lines, and seems to not have very good brakes, pedal went to far and it steered bad.

got a new MC and bled it, then bled my lines again. will build pressure great and then you let off for about 3 seconds, and go to push it in again, and it hits the floor for like 5 pumps..

checked for leaks everywhere, replaced MC again (warranty). TRIED starting the truck, and did no difference. i figured if one of my lines were leaking i would still have brakes on either front or rear but i lose them all. so im thinking its the proportioning valve back to the MC somewhere.

i dont understand this also, if i pump it up and let it go like i said above then try it again i lost it all, but if i only let it up like 3/4 the way and push down again, ive got pressure still. keep in mind this is the 3rd MC ive returned to O reilys as a warranty


has anyone ran into this problem? my flare fittings look fine also. using the pump and crack the bleeder screw method

[geezer#99]

Did you bench bleed the master before putting it on. Or bleed it on the truck before hooking up the lines. Start bleeding the lines from the farthest cylinder back to the master.
Did you depress the plunger on the prop valve when you bleed the back.

[Dillon79scotts]

Originally Posted by geezer#99

Did you bench bleed the master before putting it on. Or bleed it on the truck before hooking up the lines. Start bleeding the lines from the farthest cylinder back to the master.
Did you depress the plunger on the prop valve when you bleed the back.

I have never done anything with prop valve. I tried pushing on it but wouldnt move
Posted via Mobile Device

[geezer#99]

Should be a cap on the end that covers a small plunger. You need to depress the plunger and keep it depressed in order to bleed the brakes. You might need to make a bracket to hold it in.

[Dillon79scotts]

Originally Posted by geezer#99

Should be a cap on the end that covers a small plunger. You need to depress the plunger and keep it depressed in order to bleed the brakes. You might need to make a bracket to hold it in.

you have to depress it? i have never had to do this before bleeding brakes on similar trucks

[cdowns]

Originally Posted by Dillon79scotts

you have to depress it? i have never had to do this before bleeding brakes on similar trucks

that is why having and reading a factory service manual you get to find out the proper way how to do the job

[Wrenchbender Ret]

You have too much clearance between the shoes & drums. You need to adjust the brakes. I dont know what syatem you have but adjust each shoe till you get a heavy drag & back it off about 4 notches. You may still have some drag but they will seat in.

[68gmsee]

A few questions:
What parts did you replace besides the master cylinder?
Do you have power brakes?
Also, I know you said proportioning valve but do you have disk/drum or drum/drum?

I just did a complete drum/drum brake job on mine and it stops the best it ever has.

Here's the parts list:
Master cylinder
Brake shoes
Spring kits
New rubber brake hoses 2 in front and 1 in back
Turned all the drums -$7 each

I bench bled mc, bled brakes and I adjust them as Wrenchbender posted.

... pumping "up" suggests air still in the system.

[Dillon79scotts]

Originally Posted by Wrenchbender Ret

You have too much clearance between the shoes & drums. You need to adjust the brakes. I dont know what syatem you have but adjust each shoe till you get a heavy drag & back it off about 4 notches. You may still have some drag but they will seat in.

okay so you even think that with my brakes doing this this is my cause?

i pump it up to bleed the brakes, no matter which brake im bleeding, it will do this even after all are bled.

pump it up and get the peddle pretty firm. stop pumping for no more than 3 seconds, and next time i go to push the pedal down, there is only a little resistance and it will go to the floor easily for another 5 pumps to build pressure again.
but

if i pump it, get the peddle firm again, and only let it come 3/4 the way up and hold it there for seconds, or even minutes, i still have pressure on my pedal.


I have disc front, drum rear.
have replaced one caliper, checked the other. havent replaced rubber lines, because my brakes were working to a point... before i went to change the MC. and worked great before my 3/4 ton swap

[Longhorn Man]

If you pump them up and hold the pedal, one of two things will happen, and this will tell us whats wrong.
If the pedal stays up the whole time you keep pressure on it, then you need to adjust the shoes.
If it bleeds down while holding the pedal, then you have an internal leak, or external leak, or air in the lines.

[Dillon79scotts]

Originally Posted by Longhorn Man

If you pump them up and hold the pedal, one of two things will happen, and this will tell us whats wrong.
If the pedal stays up the whole time you keep pressure on it, then you need to adjust the shoes.
If it bleeds down while holding the pedal, then you have an internal leak, or external leak, or air in the lines.

i can pump it and hold it where it is firm till my leg will fall off. it stays firm if i dont let it come back up all the way

[68gmsee]

You got power brakes? Just curious...

[Longhorn Man]

adjust the shoes on the rear axle.

[Dillon79scotts]

Originally Posted by Longhorn Man

adjust the shoes on the rear axle.

thats what i ended up doing, finding i had a bad wheel seal and worn brakes anyways, the wheel cylinder was wet, im pretty sure was brake fluid so im replacing it. pulling off passenger side tomorrow.

[Dillon79scotts]

yes power brakes

[Dillon79scotts]

i believe i got my brakes working now, a rear wheel cylinder was leaking a little bit.

replaced both just to do it.

held pressure fine, but i need to loosen the rear brakes for sure.
going to check back tomorrow and see if it wont hit the floor again

[lil hoodlum]

Oh boy! The joys of working on the brake system. I feel for you. My first project on my truck many, many years ago was "fixing" my brake system. Each time a replaced a part the brakes worked a "little" better. By the time it was all said and done, I had replaced the entire system. LOL

My saving grace was that I had a room mate at the time who spent countless hours in seat time pumping the brake pedal while I was underneath opening and closing bleeder valves.

I hope everything works out for you in the morning.

When you get it all working as it should, let us know how you like the 3/4 ton gear.

Good luck!

Keith

[magwakeenercew2jh]

Originally Posted by geezer#99

Should be a cap on the end that covers a small plunger. You need to depress the plunger and keep it depressed in order to bleed the brakes. You might need to make a bracket to hold it in.

A medium sized "C" clamp works.

[Dillon79scotts]

Originally Posted by magwakeenercew2jh

A medium sized "C" clamp works.

i couldnt really get one in there, i tried depressing it and got it to move a little with channel locks. so i tried bleeding that way and i guess it worked.

i think i still need to adjust my brakes tho, because when it hits the secondary "clunk" in the pedal for the rears i guess it would be its just a rock solid hit, and wont move so im thinking one side is still touiching the drum