Brake Issue

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Feb 5, 2007 | 05:38 PM

D3thM3tal

Thread Starter

Tuned

Joined: May 2006

Posts: 494

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From: Twin Cities, MN

Brake Issue

I have good pedal pressure with the truck off. As soon as I start the truck, the pedal becomes very spongy and only slows the truck withinth the bottom 2 inches of pedal travel. Truck is a 95 F-150, I believe its got ABS on the rear wheels. I rebuilt the rear end completly last year with new components and have taken the drum covers off and inspected for fluid loss, there is none. The front calipers leak no fluid as well, I have bled the crap outa the fronts and rears to no avail. I am not leaking or loosing any fluid after driving it around and applying the brakes. I do not think any fluid is leaking into the booster because I do not have any forign smells from the exhaust or am I loosing any brake fluid.
Any ideas?

Feb 5, 2007 | 06:20 PM

xltlariat87

Senior User

Joined: Mar 2004

Posts: 217

Likes: 1

From: southwestern,pa

sounds to me , that your back brakes need to be adjusted tighter. they may not be making enough contact with the drum. check your self adjuster's. they may be stuck.

Feb 5, 2007 | 06:25 PM

velcro7279

Tuned

Joined: Oct 2003

Posts: 446

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From: Grayling, MI

Could be your RABS valve. It is what controls the ABS in the rear. I think they are about $125. I by-passed mine when it went bad. My symptoms were similar to yours. The front brakes were the only ones stopping the truck. I replaced my MC and had checked or replaced everything else. I found out about it from this forum. Maybe do a search to see if you can find more info on diagnosing it.

Steve

Feb 6, 2007 | 05:18 PM

D3thM3tal

Thread Starter

Tuned

Joined: May 2006

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From: Twin Cities, MN

Well I checked both rear drums, and fixed the passanger side. The adjuster had fallen off. I adjusted both rear brakes all of the way out and bled them. I also bled the fronts. I'm thinking its possibly the RABS valve, maybe it has air in it? What I still dont understand is that when the truck is off, I get very firm pedal pressure but as soon as I start the truck I loose all the presure i the pedal. Is the booster possibly magnifying a problem? If there is air in the RABS valve, would it cause my to loose most of my brake power? Thing is, when I was rolling backwards down my snow covered blacktop driveway, I slammed on the brakes. When the pedal hit the floor, the rears ended up locking up and the fronts did not.

I can still stop the truck when driving, its just very gradual and it feels like most of the braking is being done by the rears... I've got a 4wd event to make this weekend and I would really hate to miss it over this...

Feb 7, 2007 | 12:38 AM

JRStraight

Freshman User

Joined: Sep 2005

Posts: 34

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From: Windsor Colorado

If the rear brakes are adjusted up, and you know there is no air in the lines, I'd have to think that the fluid is bypassing the main piston in the master cylinder.

Typically when the RABS valve goes bad, the ABS light on the dash will come on about 5 seconds after starting the vehicle.

Just my 2 cents.

Jay

Feb 7, 2007 | 01:59 AM

D3thM3tal

Thread Starter

Tuned

Joined: May 2006

Posts: 494

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From: Twin Cities, MN

Had a good friend come over and take a look. He took off the rear drum covers and found a sticking e-brake cable that I did not spot. After fixing the cable, the brakes work 100% like they should. I thank everybody who responded with accurate and good information, you people rock!

Feb 7, 2007 | 05:44 AM

velcro7279

Tuned

Joined: Oct 2003

Posts: 446

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From: Grayling, MI

Quote:

Originally Posted by JRStraight

When my RABS valvewent out I didn't have any light on the dash at all. Which is why I ended up replacing the MC first before I bypassed the RABS valve. I actually had no brake warning lights at all. All of the lights work, too. Go figure.

Steve