abs brake problem, ford can't help

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Nov 21, 2000 | 01:27 AM

trucke

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abs brake problem, ford can't help

I have a 89 f250 supercab, camper special 460, rodomatic, stock suspenstion, and stock tires: problem is i have excessive pedal travel, weak brakes, and they will lock up when you apply light pressure, and will not release for a short period, and in some cases the brakelight/rabs light will come on, ford can't find any problems with the system, it has been in several times, and i am a mechanic myself, i have no clue other than the rabs valve, but ford says it could not be, i did find a tsb that mentioned about rear braking problems, but it was just a bullitin, and not the real tsb. anybody have any ideas, or know what the h--- is going on here, any idea would be of great help, two heads are better than one. thanx

Nov 21, 2000 | 10:48 PM

PAUL_2

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abs brake problem, ford can't help

You can always point out the Tsb to the Ford tech , They can have a look at it & tell you if it applies to the problems you are having . If the rear brakes are locking up , not releasing then first check the condition of the rear brake shoes & all the associated hardware . Is the problem more prevalent during wet / cold weather ? Also lubricating the backing plate where the shoes make contact help them to release properly .

Nov 22, 2000 | 04:22 AM

trucke

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abs brake problem, ford can't help

paul thanx for the reply! the brake hardware, shoes ect have been replaced, and auto adjusters have been replaced, and working properly, also backing plate has been greased, and master cyl has been replaced. as for if it is more of a problem in warm weather or cold, wet or dry it really dont seem to make a differance that is what is so baffling about it and it will do it when you just cant get a trouble code ie in traffic ect, one question i had is in one of the archives i read that someone had disabled the abs system somehow ie disconecting a plug or plugs do you have any idea about that? that way i could see if it is the abs or the natural brake system, prosess of alimination seems at this time the only way to find the problem. thanx for the reply, as i said before any thoughts can help sometimes you get so indepth in diagnosis that you miss the obveious

Nov 22, 2000 | 06:51 AM

PAUL_2

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abs brake problem, ford can't help

The only other suggestions I can come up with is for you to check the vacuum booster . With the engine off pump the brake pedal several times to eliminate the vacuum , start the engine & the pedal should move down , if not then the vacuum booster may be the problem . Since your vehicle is set up for a camper does it have the Height Sensing Proportioning Valve ? I looked thru my diagnostic chart & for Brakes grab or lock up when applied one of the possible problems was the Rabs Valve . Does having a load such as a camper make any difference ?

Nov 22, 2000 | 10:16 PM

jakegypsum

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abs brake problem, ford can't help

Sounds very much like a rabs problem. I had a very similar problem 2 months ago with my 92' f-250. Replaced front brakes, rear shoes, and the master cylinder. Still, the truck was not proper. Myself and two other mechanics were stumped. I posted the problem on this site and Paul got back to me. It was the rabs valve. My rabs warning light never lit up until the day before I replaced the valve. Crazy. A Ford dealer charged me approx $150.00 for the valve plus a core return of approx $135.00. That little valve gave us the run-around like you would not believe. Good luck.

Jakegypsum // Ford fleet, soup to nuts.

Nov 27, 2000 | 08:52 PM

trucke

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abs brake problem, ford can't help

thanx for your reply on my message board, now all i need to do is just get off my butt and fix it thanx again

Jun 26, 2001 | 01:07 PM

kwing

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abs brake problem, ford can't help

I have a similar problem to jakegypsum in that the brakes fade off until i am at a full stop. All brakes are new, including hardware and a new (not rebuilt) master cylinder. System has been professionally bled twice. My additional symptom is that on every other stop the front brakes pull hard to the left OR hard to the right, indicating an air bubble in the system somewhere??? or could it be the RABS valve or a bubble stuck in the proportioning valve. All other brake components and hoses are fine.