help with brake problem
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help with brake problem
I just got a 76 f150, power brakes , new front rotors,new master cylinder. While driving the brakes will out of the blue occasionally firmly drag, when I pull over the brake pedal is very tight with no play at all. I shut the truck for a few seconds and everything goes back to normal with plenty of play in the pedal. Thanks in advance for your help
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Someone may have miss adjusted the brake rod behind the master cylinder ....It may not be opening the return ports for the fluid .. Loosen the nuts holding the master cylinder in place , see if the problem goes away ...
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From: Denver Metro Area, CO
I would disconnect the vacuum line to the power booster, cap it off (plug the hose) and then see how the brakes are.
The pedal will be hard because there's no power assist but it should be consistent.
Have you looked at the rear brakes at all?
The pedal will be hard because there's no power assist but it should be consistent.
Have you looked at the rear brakes at all?
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All it does is assist ...
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From: Denver Metro Area, CO
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He says everything goes back to normal after shutting off the engine (although he says nothing about restarting the engine or and when the brakes return to normal in relation to that event), this makes me suspicious of the power brake booster (which runs from engine vacuum).
If so the check valve may be an issue ...If that is the case , it will affect all front & rear ...
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After shut down I feel the pedal go back to normal restart and everything is ok. I was leaning more towards something to do with the booster (though I admit that I don't know if how or why rhats possible). Here is why I think booster
The problem is intermittent
I can sit parked and running and pump the brakes all day and they bleed down with no problem
The problem comes on its own, not from mr applying the brakes
Thanks again
The problem is intermittent
I can sit parked and running and pump the brakes all day and they bleed down with no problem
The problem comes on its own, not from mr applying the brakes
Thanks again
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You were correct, disconnected booster and problem solved. Thank you. If you have any in site as to how the booster would cause this problem I would be very interested
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Oh yeah. But would like to know how the booster could cause my described problem
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With the vehicle not moving, the only effect the engine not running has on the brakes is the removal of vacuum from the power booster.
(My question about the back brakes was never intended to be related to the booster, I was merely wondering if work had recently been done there or if perhaps it needed to be - a mechanical problem back there can definitely affect the pedal.)
Anyhow, disconnect the vacuum and the brakes are fine, logic tells me the problem is in the booster/MC/pedal area and not at the drums or calipers.
Most vacuum-operated power boosters are essentially the same and look something like so:
For descriptions of how these things work, read:
Hydraulic brake - Wikipedia, the free encyclopedia
Classic Chevy, Chevrolet, GMC, Ford technical articles
Troubleshoot Power Brakes
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Ctubutis, thank you very much for your help. I still have not had a chance to check the rear brakes. Like you I believe that the problem is limited to the booster being that there has not been a problem of any kind since it being disconnected. Thanks again