Archived Low brake pedal

[SMalafy]

I have a 95, 2500 4x4. The brake pedal started getting low so I checked my pads and shoes. They checked out alright so I adjusted the rear shoes although they were not to far out. I looked for leaks in the lines although I was not losing any fluid and also bled the whole system, still a low pedal when I start the truck up and go to put it in gear. The pedal goes very low but the red light does not come on. Finally I changed the master cylinder as the original had 183 K on it, figuring that was the culprit. Still the same results. I'm stumped, anyone have any ideas of things to check ?

 

[FourBarR]

not that informed on 95 model. I understand they have a vacuum type boost system. someone with a 95 will chime in to confirm .

 

[Joe G.]

Check for a vacuum leak. The problem may be in the brake booster.

 

[B.G. Smith]

Try this. Start the truck, apply the parking brake, pump the brake pedal a couple of times, the pedal position shpould gets higher, with the parking brake still engaged, wait about a minute and hit the pedal again, if you have good pedal then there is still slack (need more adjusting) in the rear brakes. bg

 

[SMalafy]

If the brake booster was bad, wouldn't the pedal be hard and high ???

 

[Joe G.]

If I'm doing a lot of brakeing at low RPM I loose some pedal when the vacuum can't keep up.

 

[Nightram]

Does it have ABS? I know Furd's where notorious for the ABS pump solenoids to bypass and then you have like no pedal feel, goes right to the floor. How did the wheel cylinders look?

 

[B.G. Smith]

If the brake booster was bad, wouldn't the pedal be hard and high ???

Yes, if you had normal brakes and a high pedal and the vac. booster quit the pedal would still be high, just very hard to push. bg

 

[SMalafy]

Wheel cylinders and brake shoes were replaced last year and yes it does have ABS. There is plenty of vacuum going to the booster too. The pedal will stay hard until I start the truck, then when I step on the brakes it goes to the floor.

 

[B.G. Smith]

Wheel cylinders and brake shoes were replaced last year and yes it does have ABS. There is plenty of vacuum going to the booster too. The pedal will stay hard until I start the truck, then when I step on the brakes it goes to the floor.

For the pedal to go to the floor you have to have either air in the system, a bad master cylinder (bypassing inside), a fluid leak to the outside somewhere or the rear brakes are too loose. If you had a leak the brake light should come on. Even with some air in system or rears out of adjustment, you should be able to pump up some pedal? ow did you determine how tight the rears were, best way is with both rears off the ground, tighten until you can't turn the wheel then back off about ten clicks. I have yet to see an ABS system that will cause the pedal to go to the floor unless there is a leak to the outside. Are you losing fluid? Did this start suddenly or gradually got that way?

 

[SMalafy]

For the pedal to go to the floor you have to have either air in the system, a bad master cylinder (bypassing inside), a fluid leak to the outside somewhere or the rear brakes are too loose. If you had a leak the brake light should come on. Even with some air in system or rears out of adjustment, you should be able to pump up some pedal? ow did you determine how tight the rears were, best way is with both rears off the ground, tighten until you can't turn the wheel then back off about ten clicks. I have yet to see an ABS system that will cause the pedal to go to the floor unless there is a leak to the outside. Are you losing fluid? Did this start suddenly or gradually got that way?

Yes I can pump up some pedal, but it does not stay up too long. The master cylinder was changed with a remanufactured one. It must be air because I am not losing fluid. I'll trybleeding again and see what happens, although this will be the 3rd time i've done it.

And yes I did bleed the master cylinder before I put it on.

 

[B.G. Smith]

Check the position of the bleeder screws on the front calipers. I saw a situation once where a friend of mine took his truck to a shop to have some brake work done, the mechanic swapped sides with the calipers resulting in the bleeders being near the bottom of the calipers, the mechanic could not figure out why he couldn't get a pedal on the brakes. bg

 

[Rhondasway]

I don't know if this is relevent, but I had brake problems when my power steering fluid was extremely corroded. Just a thought... How does your steering act? I think your brakes are like mine, with the booster connected to the power steering. I flushed mine with Valvoline Synthetic until it was clean and it made a world of difference to steering and brakes.

You're bleeding them "right" also, I assume...

 

[SMalafy]

Power steering fluid was changed last year and I used a mighty vac to bleed the brakes, and also tried the hose submerged in fluid, type bleeding too. I'm starting to think something is screwed up with the ABS.