Brake Problem or not ??
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Junior User
Joined: Aug 2008
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Brake Problem or not ??
I Just bought a 1993 Ford F-350 7.3 NA. After checking it over the brake pedal felt funny compared to my 88 f-250 gasser. I checked for leaks at wheel cyl and hoses and lines nothing, Checked the vacuum at the booster 25Hg. Pedal feels fine with the engine off no drop maybe 2 inches of travel, start the engine, foot on brake slowly goes about 2 inches off the floor, brakes work good, but sucky pedal, So I figured the booster was bad replaced it, same story. Looked at a couple of google serches and some say its normal and ford had a name for it on trucks with a vacuum pump they called it step-through. Is this as good as they will get?
Post Fiend
Joined: Nov 2004
Posts: 5,638
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From: Manitoba
When bleeding brakes do not forget the RABs valve on the frame, done after rears and before fronts. Are you pressing normally or extra hard when stopped....... just press it like you would at a stop light........problem may go away after rears are adjusted.
2 quick ways to adjust rears: (1) use the park brake (both sides must be operational) with release handle pulled (just keep pumping it) or (2) back up truck 10 feet stop hard and drive ahead and stop...... repeat until brake pedal is up higher in both cases. You can also use the adjusters in the backing plate (requires rear wheels off the ground)..
2 quick ways to adjust rears: (1) use the park brake (both sides must be operational) with release handle pulled (just keep pumping it) or (2) back up truck 10 feet stop hard and drive ahead and stop...... repeat until brake pedal is up higher in both cases. You can also use the adjusters in the backing plate (requires rear wheels off the ground)..
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Junior User
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help
I would agree on air in system but they pump up and hod ok when the truck is not running, and Ive gone through 1 gallon of fluid bleeding them. It only sinks when the truck is running??????? Help
Elder User
Joined: May 2004
Posts: 790
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From: Danville, Pa
bad master cylinder? I know when the o-ring seals go between the front and rear pistons, you wont loose fluid, or gain air, but the pressure bleeds from one circut to the other causing the same symptoms.
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Junior User
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Junior User
Joined: Aug 2008
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as of now im reall at my wits end. New master cyl new booster, rear wheel cyl, 2 gallons of brake fluid. Same D!@N thing. I really dont know where to go from hear?
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Post Fiend
Joined: Jan 2005
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Can you describe a little better what is happening. With engine running does the truck brake to a stop with a couple of inches of pedal travel and then if you press pedal harder it quickly goes to the floor? If so then you still have air in the system. However when truck comes to a stop does the pedal sink down slowly with just the normal pedal pressure? If so you have a faulty RABS valve. If you think it is the RABS valve post back and I will tell you how to eliminate it from the equation.
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Junior User
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When you come to a stop it stops normal then with a little extra effort it goes slowly to the floor. In a panic stop it will stop but the pedal ends up 2 inches from the floor. Im bypassing the RABS valve now, to see if that will help.Kee the suggestions coming
Post Fiend
Joined: Jan 2005
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Worth a try. However you don`t have to bypass the whole valve. If you unscrew the large hex plug on the end of the valve, remove the spring and replace the hex plug you have then bypassed the valve that is probably faulty. Then give the pedal a few pumps to fill the chamber and see if it has made any difference. If it solves the problem then you can either leave the spring out and do without RABS or fit a new or reman RABS valve body. If it does not solve the problem then just replace the spring and look elsewhere. Hope you get it fixed.
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Junior User
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Its not air because the pedal is fine when truck is off. If there was air the pedal would be spongy and its not from what I've read on other forums this is a problem and ford never acknowledge. But no one can tell me how to fix it, a long time ford tech said he new a guy that could fix it and he will call him tomorrow and let me in on the big secret.