Brake Troubles! Help!
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Senior User
Joined: Nov 2002
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From: chicago
Brake Troubles! Help!
My buddy just bought a 78 F150. The brakes were shot. He had a hard pedal and poor brakes the entire way home. We replaced the booster. Now pedal was low, no pressure. So we replaced the master cylinder, front pads, rear shoes, rear wheel cylinders. We bled them several times. We have a good shot of fluid out of the bleeders when he pumps the pedal 5 timesand holds it while I open them up. Still, pedal goes to the floor, and it seems as if the front brakes are not working. When you slam on them, the rears lock. The rear shoes are adjusted properly. The only think I can think of is the proportioning valve is bad. I have done a lot of brake jobs, and have yet to encounter a problem with the proportioning valves. But I am out of ideas! Help
New User
Joined: Jan 2008
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This is confusing.
are you saying that now since you have replaced booster & the M/C, the pedal goes to the floor ...the rears work but the fronts don't ?
Maybe the front calipers are seized ?
Were the pushrods set to spec when everything was fitted together ?
are you saying that now since you have replaced booster & the M/C, the pedal goes to the floor ...the rears work but the fronts don't ?
Maybe the front calipers are seized ?
Were the pushrods set to spec when everything was fitted together ?
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Senior User
Joined: Nov 2002
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From: chicago
When he first bought it(ebay), he picked it up knowing the truck needed brake work. His pedal was super hard, and the trucked barely stopped. So he figured booster. So his mechanic replaced the booster without opening the hydraulics of the system(left MC lines on). Picked truck up, now it had a weak pedal. Pedal basically had very little pressure, and would go to the floor. When stopping hard, the rears would lock. Then we figured to replace the MC. While we had it apart, al the shoes/pads were shot, replaced them and wheel cylinders( one leaking). Bled brakes numerous times, still, pedal doesnt have much pressure at all, and the braking sucks. Pedal will go to the floor. Calipers are grabbing, we spun the front wheels off the ground and when the brakes were applied and it stopped.
One thing I noticed is that the little bleeder pin on the proportioning valve is in the out position. Well at least i think it is. It sticks out about 1/4". I tried to push/pul on it but it wont move. Also, looks pretty corroded. Feels like rust under that little rubber boot that surrounds the pin.
One thing I noticed is that the little bleeder pin on the proportioning valve is in the out position. Well at least i think it is. It sticks out about 1/4". I tried to push/pul on it but it wont move. Also, looks pretty corroded. Feels like rust under that little rubber boot that surrounds the pin.
New User
Joined: Jan 2008
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Okay what about the calipers on the front?
Were they checked for being seized ?
Rubber Brake hoses checked for fluid travel ?
NOTE: Not every NEW master cylinder is guaranteed to work properly.
One person on here went through 5 of them for 2 different parts houses to get a good one.
Spray the pin with a good penetrating fluid ( Not WD-40)
Booster Push rod measurement ?
Is it correct ?
Were they checked for being seized ?
Rubber Brake hoses checked for fluid travel ?
NOTE: Not every NEW master cylinder is guaranteed to work properly.
One person on here went through 5 of them for 2 different parts houses to get a good one.
Spray the pin with a good penetrating fluid ( Not WD-40)
Booster Push rod measurement ?
Is it correct ?
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Senior User
Joined: Nov 2002
Posts: 163
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From: chicago
Originally Posted by Mil1ion
Okay what about the calipers on the front?
Were they checked for being seized ?
Rubber Brake hoses checked for fluid travel ?
NOTE: Not every NEW master cylinder is guaranteed to work properly.
One person on here went through 5 of them for 2 different parts houses to get a good one.
Spray the pin with a good penetrating fluid ( Not WD-40)
Booster Push rod measurement ?
Is it correct ?
Were they checked for being seized ?
Rubber Brake hoses checked for fluid travel ?
NOTE: Not every NEW master cylinder is guaranteed to work properly.
One person on here went through 5 of them for 2 different parts houses to get a good one.
Spray the pin with a good penetrating fluid ( Not WD-40)
Booster Push rod measurement ?
Is it correct ?
New User
Joined: Jan 2008
Posts: 0
Likes: 24
That doesn't mean they are working (pushing out and applying the pads to rotor), that just means the MC is doing its job and fluid is getting to and coming out the piston chamber. Possibly seized.
There has to be easy travel of the pistins ....both directions
After doing all that you did, I can't believe you never replaced the calipers.
They cost $12.00 each w/core
Replace the calipers and get back to us.
There has to be easy travel of the pistins ....both directions
After doing all that you did, I can't believe you never replaced the calipers.
They cost $12.00 each w/core
Replace the calipers and get back to us.
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Elder User
Joined: May 2006
Posts: 636
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yeah calipers are cheap, i have to reaplce my drivers side one eventually. try that to see if it works, if not then look into the valve since it is pricey
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Laughing Gas
Joined: Dec 2000
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From: East Texas
I just went through the same thing on my '77. Very stiff calipers. Like Dennis said, the calipers should move smoothly. Reman calipers for it were ~$12 each. One thing, as long as you're in there, you might go ahead and replace the brake hoses as well. Once they get old, they could collapse internally which could in turn inhibit the flow of fluid. The hoses for my '77 were about $13.00 each.
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