F150 MUSHY BRAKE PEDAL

1985 Ford F-150

Tiny

skyhawk54149

August, 8, 2009 AT 8:28 AM

Brakes problem
1985 Ford F150 V8 Four Wheel Drive Automatic 101000 miles

I have replaced the vacuum assist, master cylinder, both rear wheel cylinders, and both front calipers along with all new rear shoes, and new pads for the calipers.
After first priming the new master cylinder, all the lines were bled out starting at the right rear, then the left rear, then the right front, and last the left front. After all the air is out of the lines, the pedal is solid and the truck has good solid braking action.
After the truck has sat for a few days, the brake pedal engages the brakes right away when depressed, but then the rest of the pedal beyond that is like stepping on a soft basketball, and the braking is very poor!
I have inspected the entire brake system from front to back and see no evidence of any leakes anywhere.
After bleeding the entire system again the brakes will be good, and again after the vehicle sits the pedal will become soft again.
There are no anti-lock brakes on this truck, so I should be able to leave skid marks, but the brakes will not lock up! This has been driving me crazy!

FOUND 918 RELATED QUESTIONS

Excessive Brake Pedal Travel

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Brake Pedal Sinking

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3 Answers

Tiny

merlin2021

August, 8, 2009 AT 11:45 AM

Does the pedal pump up?

Tiny

skyhawk54149

August, 8, 2009 AT 10:48 PM

Yes, the pedal will pump up rock solid and when the pedal is held there is no " drift". After the vehicle sits a few days it gets " soft" again.

Tiny

merlin2021

August, 9, 2009 AT 7:32 AM

First, check rear shoe installation, make sure primary(short) shoe is to the front on both sides, and rear brakes are propperly adjusted. Then make sure the right type pad is installed on the front brakes, and linings are to rotor! Not the steel web. Then have someone push down on the brake pedal SLOWLY, and you watch for " turbulence" in the reservoir. Compensating port of the master may be blocked if you dont see the swirling!

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