hard braking, please help - Ford Powerstroke Diesel Forum
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Old 07-08-2013, 04:31 PM
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hard braking, please help

Problem with my f250: coming to a stop initial braking is fine and works as expected, but if I let up on the pedal and reapply the brake goes stiff as a rock. If i keep my foot on the pedal it slowly gets softer (10 seconds or so). Everything goes back to normal once Im on the gas again for a few seconds.

Booster and master cylinder were replaced this weekend. All lines bleed.

Vacuum appears to be okay at the booster (using my thumb).

WHat else should I be looking at?
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Old 07-08-2013, 06:26 PM
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Vacuum pump, or loose serp belt. Maybe it pulls on your thumb with no load, but hit the brakes a few times and it overwhelms the pump. The 10 second thing is the vacuum pump just catching up to the load.

Does the red BRAKE(!) warning light go on when this happens? Does the light work; does it go on with the parking brake and/or when you turn the key to RUN (engine off)?
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