Bronco Brake Problems

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Feb 13, 2001 | 12:05 PM

dragonman

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Bronco Brake Problems

I have a 1989 Ford Bronco with rear anti-lock brakes. The brake pedal feels fine until I start the engine. At that point the pedal goes to the floor. I have replaced wheel cylinders, master cylinders, front calipers, put on new pads and shoes, and front brake lines. The power brake booster seems to be okay since the brake pedal fades slightly when started but then the pedal goes to the floor afterwards. Air also escapes from the booster when I take the vacuum hose off. I have bled all bleeders including the antilock bleeder till I'm blue in the face with the same results. Good pedal til I start the engine. There are no leaks anywhere. Any help you can give me will be greatly appreciated.

Feb 13, 2001 | 10:45 PM

ummduh

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Bronco Brake Problems

You either have aLOT of air in the system, or a bad master cylinder.

Bleed the hell out of the brakes, i'm talking run a few gallons through. Make sure all the threads stay dry, you might wanna use a petroleum-safe teflon tape on all fittings also. Bleed bleed bleed.
Have someone pump the brakes while your underneath (preferrably at night) with a flashlight, and watch for leaks. (it'll spray a VERY fine mist, it should shine from the flashlight)

If that fails, go get another master cylinder. If you got a reman, they really don't have the best track record.. Did you bench-bleed it really well before you installed it?

Feb 14, 2001 | 08:18 PM

dragonman

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Bronco Brake Problems

[font size="1" color="#FF0000"]LAST EDITED ON 14-Feb-01 AT 09:21 PM (EST)[/font][p]I bench-bled the master cylinder until no more air was in the lines. Tonight I tried another mastercylinder with the same results-good pedaluntil i start the engine. I almost am now convinced that the problem must be in the power booster, since I lose the brake pedal with the engine on. Thanks for your response.I gotta get this fixed soon before the better half insists I get rid of it. I read that they make a power booster that you have to adjust the rod on and one that comes preadjusted. does anyone know if this is true or where the best place to get one is.

Feb 14, 2001 | 09:08 PM

ummduh

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Bronco Brake Problems

Well, how far does the pedal go down without the engine running? It should only go down about 1 to 2 inches, then about double that with the engine running. If there is more than a half inch of free-play in the pedal before you meet resistance(the brakes actually start moving), the adjusting rod is out of whack.

The booster generally won't make the pedal go to the floor, you simply have much more brake effort. But the fact that ther pedal goes to the floor when the booster works, when it's multiplying pressure, means that it's forcing the fluid much more, possibly finding leaks that aren't there without the added pressure. (get that?)

Are the rear brakes adjusted properly?

Feb 14, 2001 | 10:29 PM

iknowitall

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Bronco Brake Problems

I have the same problem with my 89 bronco . There was air in the lines. The peddle would sink to the floor scared the hell out of me. There is a rubber tube going into the right side of the rear axel it's part of the rear brakes make sure that it hooked on nice and tight. It gets out after awhile sometimes. I hope this is the case. I noticed with my bronco the dealers do great jobs on the brakes compared to the regular shops. Just make sure your very nice to them and don't try to make them cut down a fair price otherwise your gonna have a lot more problems than the breaks. Thats a fact

Feb 15, 2001 | 09:30 AM

russ10

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Bronco Brake Problems

Feb 22, 2008 | 03:57 PM

SHO1992

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I have an 89 302efi replaced all the break shoes/pads, calipers,MC(Bench Bled), bled the whole system 3x's. When not running I can get the pedal to pump up then when you start the truck right to the floor and no breaks. The rear brakes have a proportioning valve bled that, no leaks any where on the truck. The front break lines go from the MC to I'm guessing some sort of metering block, one line in from MC, 2 lines out one to each front caliper. The only thing I haven't F'd with yet is the booster. I guess I could have a bad MC out of the box, from reading some of the other brake horror stories anything is possible.