Mechanics

F350 PEDAL GOES TO FLOOR

1994 Ford F-350

Brakes problem
1994 Ford F350 Two Wheel Drive Automatic 90000 miles

I have a f350 dually diesel. The brake pedal goes to floor when engin is running. Ok when motor is off. New master cylinder, bench bled, no leaks in system. Full system bled three times, all brakes adjusted and in good condition. The shop I had the work done at has no idea.
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Duainet
June 22, 2010.



Hi
Was pedal going down the original problem? If yes problem in Hydro-boost accumulator leaking down.
Pedal go down slow when pressure applied? Do brakes apply?
Let me know
Thanks for donate

Docfixit
Jun 22, 2010.
Yes the pedal went down in the begining. They started with the master cylinder. The brakes apply when depressed and pedal slowly goes to floor

Tiny
Duainet
Jun 22, 2010.
On my brake system I have a vacumn booster behind the master cylinder so I don't think I have a hydro booster accumulator

Tiny
Duainet
Jun 22, 2010.
Thought it was superduty many 350 are so try this apply parking brake not full on but say 5 clicks does pedal not fall or go slower?

Docfixit
Jun 22, 2010.
With parking brake on half way does not make a differents still creeps to the floor when pedal is applyed

Tiny
Duainet
Jun 22, 2010.
Checking break pedal reserve engine idling pump pedal 3-4 times the off pedal wait 15 sec. Now apply brake pedal untill it stops. Now raise engine RPMS to 2000 then release accelerator as engine returns to idle brake pedal should move downward. If not check vacuum pump

Docfixit
Jun 22, 2010.
The problem is when you wait the 15 sec. Then reply pressure it dosen't stop it just goes slowly to the floor

Tiny
Duainet
Jun 22, 2010.
This my last idea was the porportioning valve on the new master cylinder or reused from old one?

Docfixit
Jun 22, 2010.