brakes

[1992f250idi]

im having a horrible time getting brakes in my truck. the line from the abs to the rear axle was blown when i bought it so i replaced that and the everything back brake wise except the drums. so then i bled everything, RR LR ABS RF LF and still no brakes. i continued to bleed until i had bled 2 of the big bottles through and it didnt change. i have good peddle when its not running, but then when i start it i lose it all. i tried unhookiung the vacuum line on the booster and the brakes will hold pressure and the peddles firm, however i need power brakes for stopping this truck haha. so does this sound like its the power booster? i can hear a faint hiss when i step on it while the trucks running

 

[LCAM-01XA]

Nope, ain't the booster. Did you try bleeding the brakes with the engine running?

 

[1992f250idi]

no i did not, im doing the 2 person one pumps while another bleeds method and its hard to tell the other person when to pump and when to hold over the sound of my truck, dual glass packs dont quiet it down much.

 

[franklin2]

One thing to make sure of; that the rear brake shoes are adjusted out to the drums. Jack the rear up and turn the tire while manually adjusting the brake through the slot in the backing plate. Adjust it till you can't turn it, and then back it off till you can turn it but still hear a little bit of rubbing. Do both sides, and this will make sure your pedal is as high as it can be.

 

[MR.T]

If the pedal slowly goes to the floor with steady pedal pressure, the master cylinder is almost certainly the culprit.

The vacuum booster is adding pressure to what you press via the pedal, so that may be the reason for a difference with the engine running. Sometimes a bad master cylinder will leak internally more/less depending on the pressure.

 

[1992f250idi]

One thing to make sure of; that the rear brake shoes are adjusted out to the drums. Jack the rear up and turn the tire while manually adjusting the brake through the slot in the backing plate. Adjust it till you can't turn it, and then back it off till you can turn it but still hear a little bit of rubbing. Do both sides, and this will make sure your pedal is as high as it can be.

yes i adjusted the brakes already that didnt help unfortunately. i guess ill buy the power booster/master cylinder combination just to make sure everythings all set.

 

[LCAM-01XA]

Don't buy anything just yet, try bleeding the darn thing with the engine running, I know it's a pain communicating with your pedal operator, but it's not like you're working on a tractor-trailer either, radio off and you two yelling loud does work, or get a third person to stand between you two and relay the information...

 

[1992f250idi]

well i bought one of those little hoses with the check valve in it to bleed, had my brother push the peddle until no air bubbles came out and did this for each wheel and the peddle still doesnt feel any better but if i pull the vacuum line off the booster i have good firm peddle that doesnt sink right to the floor so im clueless

 

[FoMoCo]

Re-check for leaks, with the booster engaged you are applying more pressure. It does not take much of a leak to cause pedal fade. The only bad thing is you/we have rear drums, so it is hard to tell if a slave is leaking.

 

[MR.T]

well i bought one of those little hoses with the check valve in it to bleed, had my brother push the peddle until no air bubbles came out and did this for each wheel and the peddle still doesnt feel any better but if i pull the vacuum line off the booster i have good firm peddle that doesnt sink right to the floor so im clueless

For what it's worth, I've not had good results with the check valve hoses (at least the ones from 35 years ago). Couldn't get a reliable bubble tight seal on the hose to bleed screw, air would get sucked back in. The frustration is still vivid in memory.

With the hose in a clear jar, I have the helper close the bleed screw before getting to the end of pedal travel. Bleed until at least three pedal presses in a row have no bubbles in the jar. Start with the furthest wheel away from the master cylinder and then continue in that order. No need to run the engine.

If holding the same steady pedal pressure results in the pedal slowly sinking to the floor, it's typically the master cylinder leaking internally, or an external leak in the system. Air in the system makes the pedal feel mushy, but with steady pressure the pedal does not continue to travel.

 

[LCAM-01XA]

What Mr.T said, you need to close the bleeder before the helper lets off the pedal, at least that's what I always do and it's never failed me, unlike those self-bleeder kits. Having the engine running is usually not needed, but sometimes it helps build up enough pressure to push out all these little pesky air bubbles.

 

[oldmisterbill]

Did you bleed the Rabs valve?

 

[LCAM-01XA]

Bill, he says he did, in the first post.