Pre-1987 Ford F150 Trucks Discuss your pre-1987 Ford F150 truck here.

Brake Issues

Old 02-02-2013
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I have a 1984 f150 with 302v8

I changed the front disc brakes, calipers, rotors, and the master cylinder. I bled the new mc and installed it then went to bleed each caliper bleeder and i cant because the brake pedal is sunk to the floor. When the truck is not running i have firm brake pedal as soon as i crank the truck the pedal sinks to the floor. This truck has a brake booster i have checked everything and cant seem to figure this out please help
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Old 02-02-2013
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When i block off the booster vacuum hose my brakes work
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Old 02-03-2013
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Sounds like the booster might not be receiving vacuum from the engine, possibly due to a plugged vacuum hose, a vacuum leak or a defective check valve. It can also indicate a failure of the booster itself.
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Old 02-03-2013
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I think its gettin vacuum because when i take the vaccum hose loose from the booster the truck dies. I thought if the booster fails the pedal is hard to push down?
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Old 02-03-2013
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To test for vacuum problems, start the engine and run it to medium speed, then turn off ignition and take your foot off the gas. Wait about a minute and a half and then apply your brakes. You should feel the vacuum boost on at least two brake applications. If you do not, you may have a vacuum system leak or bad vacuum check valve.
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