Sometimes, when bleeding brakes, if your pedal operator is too enthusiastic, the proportioning valve will see that as a 'circuit failure', and cut off flow to that circuit. Give a nice hard pedal.... but, no brakes on one end of the truck.

Also, that is a LONG line to the rear...... sometimes fun to get all the air out. What I generally do is, remove the bleeder valve completely, and stick my finger over the hole, then have a helper SLOWLY pump the pedal, until i get most of the air out of the line. Have helper hold pedal on floor, while I put bleeder back in, and then finish bleeding that side normally. Usually works very well.

If you end up with the proportioning valve shutting off the circuit you are working on, close all bleeders on that circuit, go to the OTHER end of the truck, have helper pump up the brakes, and HOLD it, then release one of the bleeders. This will get the p-valve to release again. Go back to what you were doing previously.

 

I'm having a similar problem- replaced the rear brakes today (I did the fronts a couple weeks ago) and bled all four wheels. After bleeding, spongy pedal and ABS and Brake light on. After a few minutes of pumping the pedal, ABS light went out. I drove for about ten minutes and braked several times in reverse to adjust the shoes. Still spongy and brake light on while driving. Removed rear drums to ensure brakes were functioning correctly- they were and and the adjuster barrels had expanded. I re-bled the entire system and was able to coax a little more air out of the rear lines. After several more times of reversing and stopping, the brakes started to firm up, but the brake light is still on.

I've read threads about people 'resetting' the proportioning valve in similar situations- I've never heard of such a thing. I've also read that if air enters the ABS system, there is a special tool required to bleed the ABS system. I did not replace the master cylinder, run the system dry, or opened up the system such that air would have entered, other than opening the bleeder valves, so I doubt that is what happened here. Is it possible that there is still some residual air in the system? If there is no air in the system, is it possibly something with the prop. valve.? The ABS light comes on like it should when the engine is started, then goes out after a couple seconds, but occasionally comes back on for a few seconds after going out but goes right out again. The brakes are to the point now where they seem normal and not spongy, and stop like they should. I'm thinking maybe I should bleed one last time, but I'm out of ideas as to what else to do.

 

Grab a friend, park friend in drivers seat. Have friend pump up the brakes, and HOLD them. Crack open a bleeder valve. (start with RR, the LR, then RF, LF) Close valve, pump up brakes again, repeat. This process will dislodge the air 'stuck' in the lines.

If the p-valve trips though, just move to the other end of the truck, and do the same thing to get it to re-center.

Make sure the line running over the gas tank isn't leaking.

Manually adjust the rears..... tighten them up so you can just here the shoes making contact with the drums. (should feel a SLIGHT resistance to turning them.)

Take it for a ride, see how it feels.

 

Okay, so yesterday I performed three complete bleeds (RR, LR, RF, LF) on the system- I probably pushed a half-gallon of brake fluid through the system. I did get some additional air out of the RR, but the rest were air-free. I couldn't see any obvious leaks on the rear line, but couldn't trace the entire run of the line over the gas tank. The brake pedal feel is as solid as it has ever been and after standing on the brake pedal for close to five minutes, it did not sink to the floor whatsoever so I don't think there is a problem in the line.

When I took the rubber cap off of the prop. valve, the pin pushes up when I depress the brake pedal- I assume this is normal? Earlier in this thread, someone mentioned pushing in the pin on the prop. valve to reset it... Is this correct?

Something is not right here and I'm beginning to run out of options. Because it's less than $10, I'm going to replace the parking brake switch in the event that it coincidentally failed at the same time I replaced the brakes but other than that, I'm not sure what to do next...

 

How do your brakes feel?

 

Brakes feel awesome- solid pedal, not mushy, truck does not pull to either side upon braking, pedal does not sink when constant pressure is applied with or without the engine running, brakes fully engage right after the pedal is depressed, brakes are not dragging, everything seems like it is functioning normal and as good as new.

My only issue is that the 'Brakes' dash light will not go out and stays on while driving.

 

Verify that the rears are working as well. If the rears seem fine, might have a look at the brake switch for the pedal...... I think they are adjustable.....

 

if the light is still on unplug the prop valve connector see if the light goes out if not its may be the ebrake switch

 

For the light, pumping the pedal in mash style multiple times is another method (if you haven't done this) to reset the prop valve. Another option for consideration maybe.

 

I'm going to really sound like an idiot here, but upon checking the parking brake switch- that is what seems to be the culprit. After changing the rear shoes, the added slack in the parking brake cable was causing the PB pedal to not fully retract and engage the switch.

Now I get to adjust the cable this weekend... Thanks for all of the help/suggestions/etc. Next time I know to check the switch first.