1982 Ford F150 6 cyl Two Wheel Drive Automatic 87000 miles
Brake resistance does not engage until pedal is about 1 inch from floor. The noise sounds more like air is escaping (leaking like deflating balloon) rather than sucking (vacuum pull) when brake pedal is depressed. The noise is loud and coming from valve boot area inside vehicle while depressing brake pedal. The noise weakens, becomes slower and shallower while brake pedal is in hold position, and stops completly when in released position.
I have tested the power booster (there IS vacuum pulling pedal away from foot when starting engine). I have come to the conclusion that atmospheric pressure is the problem since I DONT have hard pedal I assume there is no leak in power booster itself. So I am trying to understand the atmospheric filter, valve assembly and boot and I am not having any luck. Also, I can see the vacuum port seat moving back and forth with depression and I don't see any kind of atmospheric filter between the seat and the valve operating rod.
Should I be able to see the filter? Could it have rotted and fallen away? Can the valve plunger be malfunctioning and not opening and closing atmospheric port correctly? Can the poppet valve be cracked or broken and cause this problem? I havn't removed anything yet but if the leak (loss of atmospheric pressure) is being caused from one of these valve assembly parts can it be replaced or is it all internal to the power booster itself?
Wednesday, July 21st, 2010 AT 1:39 AM