yet another brake problem please help
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yet another brake problem please help
ok ive search and search the internet and still pry missed the answer so if this is a repeat post i apoligize. anyways me and my dad have totally restored a 78 f250 4x4 my question is when we start the truck up pedal goes to the floor. ok now as we were restoring this truck we got all new brake booster, master cylinder, brake lines, front brake hoses, proportioning valve, pads, wheel cylinders, calipers, basically everything that has to do with the brakes are brand new. we have bleed for days with just cracking the bleeders open to using the hose in the jar of brake fluid method with absolutely no luck. basically having no luck so im hoping someone on here can help us some how any information is appreciated thanks
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Does the pedal go to the floor when the truck isn't running? Does it stop ok?
If it goes to the floor with the truck turned off, start looking for a fluid leak at a wheel cyliner, caliper, or brake line. Partially remove the m/c and check if its leaking fluid out the rear piston seal and into the brake booster.
If it goes to the floor when you push down gradually, but firms up if you stab at it, it probably needs a master cylinder.
All of this is assuming the brakes are properly bled.
The man inside the truck is pumping the brakes up and holding the pedal while the man outside opens the bleeder, and doesn't let up on the pedal until the bleeder is closed again right?
If it only goes to the floor running, I'd suspect a booster, but that seems really unlikely. If you've tried three boosters and that hasn't fixed it, its not the booster.
Is this also a new m/c? Did you bleed the m/c before installing it? It can take forever to bleed them after they've been installed.
If it goes to the floor with the truck turned off, start looking for a fluid leak at a wheel cyliner, caliper, or brake line. Partially remove the m/c and check if its leaking fluid out the rear piston seal and into the brake booster.
If it goes to the floor when you push down gradually, but firms up if you stab at it, it probably needs a master cylinder.
All of this is assuming the brakes are properly bled.
The man inside the truck is pumping the brakes up and holding the pedal while the man outside opens the bleeder, and doesn't let up on the pedal until the bleeder is closed again right?
If it only goes to the floor running, I'd suspect a booster, but that seems really unlikely. If you've tried three boosters and that hasn't fixed it, its not the booster.
Is this also a new m/c? Did you bleed the m/c before installing it? It can take forever to bleed them after they've been installed.
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From: corbin ky
LOL sorry to say but i work at advance auto, some of the boosters are just junk right off the shelf. also when you got the replacement boosters did you get new valves on the booster? if its bad it will do the same thing, sorry i cant remember what the actual name is (have had a LONG day).
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nope good pedal when off bad when running and yes some one in the truck we run a shop out here in ohio so weve done are fair share of brakes and were totally stumped the portioning valve keeps bounceing back in forth thats why we were almost sure that was our problem ( we no this bc we got a light hooked up to the switch and it keeps sliding one way or another and other times it stays in neutral) so frustrating after spending a year and a half restoring this truck and cant drive it bc of the brakes
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If your prop valve is sliding around and giving a warning light, I'm inclined to think that you still don't have them fully bled. When I did my front disc conversion mine were a b*tch to get bled. I finally resorted to a power vacuum bleeder that a co worker had. Pressure bleeders work even better if you can get your hands on one that will work with an old school m/c res.
Also don't forget to hold out the pin in the front of the prop valve when your bleeding the fronts.
Also don't forget to hold out the pin in the front of the prop valve when your bleeding the fronts.
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You have a lot of good help on here but recheck the rear brakes. It they are not right it will make everything else act weird.
Do you have a rear brake shoe that has jumped out of the adjuster slot?
Have you adjusted the the rear brake shoes till they locked the wheels, then backed them off?
I'm sure you have bleed the rears but might recheck.
Checkout the above and if all that is correct then go back to the front half of the system.
Do you have a rear brake shoe that has jumped out of the adjuster slot?
Have you adjusted the the rear brake shoes till they locked the wheels, then backed them off?
I'm sure you have bleed the rears but might recheck.
Checkout the above and if all that is correct then go back to the front half of the system.
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