rear brake troubles

[ciffer]

I blew a brake line last fall and recently fixed it (wasn't driving it). Now both rear brakes have new lines, cylinders, shoes and hardware.

I can't get the brake firm. I had some troubles with install (long story) but I think everything is correct now. The line and master cylinder were bone dry at one point.

I bled the lines but the brakes are still squishy. The bleeders flow free just from gravity when opened and I have run quite a bit of fluid through. I back the adjusters out enough that there was a little drag installing the drums. I have backed up and stopped many times and it sounds like there is a little squeek from the rear.

Any ideas on what i should check? I don't have windows for manual adjust so I can't adjust anything that way.

 

[bradshawtech]

Trying not to assume anything here, are you "bleeding" the entire system or just the rear brakes?

You might have an issue with your proportioning valve.
You may need to rent a "power bleeder".

 

[diesel4me]

I've had to bleed all 4 wheels ,despite the fact only the rear brakes were worked on ,or lost the fluid to them due to a line leak,etc......sometimes the air will sneak into the front brakes thru the master cyl or proprtioning valve....my truck leaks the fluid out of the master cylinder's rear chamber,due to a faulty seal ,and if I let it go completely empty,I've had to re-bleed all 4 wheels to get the pedal back to "normal" again...and crack the lines at the master cyl. too,with the pedal depressed,to bleed the air out completely..

 

[chulisohombre]

sounds like you still have air in there somewhere.if you let it dry up with no fluid,the master could of locked up in one spot or the prop valve and not be moving with the fluid pressure like it should.sounds like you did the adjustment on the shoes in the rear already.does it go to the floor or firm up at the bottom of the pedal movement.if it firms up at lower pedal,does it start to slowly go to the floor?if so the master may be bad now as well.check the check valve between the intake and the brake booster and make sure you arent losing air there as well.

 

[ciffer]

I have only been bleeding the rears. it firms up then slowly goes to the floor.

 

[ciffer]

Also, on gravel the front wheels lock easily but the rears seem to do nothing.

 

[dyeager535]

Does your brake light connected to the combination (proportioning) valve work correctly?

I had a similar issue at one time, turned out my brake master cylinder had failed (likely due to it being old, and having to bleed the system) and luckily the combination valve/brake light worked, which gave me some warning.

I spent hours trying to get a firm pedal, over a few days, and finally gave up. Only a bit later did the light come on with the system all sealed up.

 

[ciffer]

When I push the pedal with the engine off the interior lamps dim slightly, I would assume that means the brake lights are working.

Edit- Or are you referring to the light on the dash? That is on all the time now.

 

[bradshawtech]

Well, there is the problem or at least one of the problems. The brake light came on on the dash because someone pushed the brake pedal when there wasn't any fluid available for the rear brakes.

You need to reset the slide valve on the proportioning valve located below the master cylinder, then bleed all the brakes starting with the longest run of lines first and working to each wheel that are closer to the master cylinder.

 

[ciffer]

Interesting, the two other times I have blown brake line the light reset itself shortly after the repair.

Anywyays, what do I need to do to reset the valve?

 

[ciffer]

It looks like there is a device mounted to the frame behind the bumper that the two lines from the master cylinder run to with two small lines running to each front brake and a larger line running to the rear. There is an electrical device on the top and a 7/16 brass bolt on the side. I assume this is the proportioning valve.

I didn't see anything that popped out at me of what I need to do except maybe something with the brass bolt, which won't turn.

I am afraid that if i try messing with that valve nothing is going to come loose and I am going to end up replacing the entire brake system.

 

[bradshawtech]

Sounds like the proportioning valve by description but I thought it was directly under the master cylinder.

Not sure how to reset the valve..... You might try to bleed the front brakes and it may reset that way.

I am sure glad I have never lived in the rust belt. I have never "blown" a brake line.

 

[imiceman44]

It looks like there is a device mounted to the frame behind the bumper that the two lines from the master cylinder run to with two small lines running to each front brake and a larger line running to the rear. There is an electrical device on the top and a 7/16 brass bolt on the side. I assume this is the proportioning valve.

I didn't see anything that popped out at me of what I need to do except maybe something with the brass bolt, which won't turn.

I am afraid that if i try messing with that valve nothing is going to come loose and I am going to end up replacing the entire brake system.

Yeah that thing behind the bumper is the Proportionning valve.
On one side, opposite of the electrical plug there is rubber button, if it's sticking out push it back in, it will reset the valve to the middle.
Bleed the brakes then check it again.
And the 1st gen trucks have that PV under the master cylinder.