Power brake issue?
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Freshman User
Joined: May 2007
Posts: 36
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Power brake issue?
Hey all,
1986 F150 351 2wd with power brakes. The brakes got extremely mushy. They would grab fine if you are quick and hard on the brake pedal, but the pedal will go all the way to the floor if you are slow and easy with it, such as pulling out of a parking space, up to a stop sign, etc. Lines bled, no change. Changed brake master cylinder, made it a little better. Now, if I disconnect the vacuum line to the power booster behind the master cylinder, the brakes will grab and the pedal feels firmer (although it takes quite a bit of effort to brake well). What's the deal with this? Why do the brakes work again when the power booster has no vacuum? If I reconnect the line, the pedal immediately returns to the floor when pressed.
Should I just replace the power booster, or is there more wrong here?
1986 F150 351 2wd with power brakes. The brakes got extremely mushy. They would grab fine if you are quick and hard on the brake pedal, but the pedal will go all the way to the floor if you are slow and easy with it, such as pulling out of a parking space, up to a stop sign, etc. Lines bled, no change. Changed brake master cylinder, made it a little better. Now, if I disconnect the vacuum line to the power booster behind the master cylinder, the brakes will grab and the pedal feels firmer (although it takes quite a bit of effort to brake well). What's the deal with this? Why do the brakes work again when the power booster has no vacuum? If I reconnect the line, the pedal immediately returns to the floor when pressed.
Should I just replace the power booster, or is there more wrong here?
Senior User
Joined: May 2007
Posts: 274
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Sounds like air in the system somewhere. Also check the flex lines they may be perished and expanding. Get someone to press the brake pedal while you look at them. Rear drum adjustment should be checked also.
You might think the brakes feel better without the booster, but with the booster working it's probably just making it much easier for your foot to compress the air that's in the system.
You might think the brakes feel better without the booster, but with the booster working it's probably just making it much easier for your foot to compress the air that's in the system.
