Brakes build too much pressure

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danboy282
Posts: 22
Joined: Sun Dec 25, 2011 5:13 pm
Location: Garden Valley, CA

Brakes build too much pressure

Postby danboy282 » Sat May 05, 2012 2:00 pm

On my 86 B2 I've been having problems with the front brakes grabbing too much. When I start out driving they fell fine, a little spongy, but fine. After driving for a short period (5-10 miles) the brake pedal gets very firm and I can feel them grabbing when i coast to a stop and when i take off, i have to burn the clutch a little more and give 'er more gas to get going. I have to bleed some fluid to relieve the pressure until the wheel spins freely. Then I refill the reservoir and test drive it and it does the same thing again.

Anyone ever had this problem or have any ideas how to fix it? HELP!

kirkland2887
Posts: 86
Joined: Sun Jan 29, 2012 6:00 pm
Location: Albion, Idaho

Re: Brakes build too much pressure

Postby kirkland2887 » Sat May 05, 2012 2:52 pm

stickiing calipers, sticking master cylinder or a kink in the line could cause these problems. what does the brake fluid look like? you could have some crap in the lines or master cylinder or caliper that is letting fluid through but won't let it return?

danboy282
Posts: 22
Joined: Sun Dec 25, 2011 5:13 pm
Location: Garden Valley, CA

Re: Brakes build too much pressure

Postby danboy282 » Sat May 05, 2012 3:02 pm

Well the fluid used to be shit, but i flushed the whole system rebuilt the calipers swapped in a used power booster and master cylinder, which made the brakes function better, but i still have the same problem.

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tekatlarge
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Joined: Tue Jan 17, 2006 8:54 am
Location: Kent, Worshington

Re: Brakes build too much pressure

Postby tekatlarge » Sat May 05, 2012 9:32 pm

I can tell you exactly what is wrong in the system

Your Flexible lies from calipers to the frame are bad. :wtf: That is a classic symptom. The lines get old and brake down internally. :eek: When you apply pressure it fills the caliper but won't let the fluid return when the pressure is released. A good way to confirm this is to jack up a front tire clear of the ground. Spin the wheel, does it turn freely? weather it does or not pump the brakes vigorously and hold the pedal for about 5 seconds. :confused: Now release the pedal and go back out to the front wheel and try to spin it. If it is stuck or hard to turn take a wrench and open the bleeder on the caliper. You should see a squirt of fluid when you open the bleeder and you should be able to spin the tire again.

Replace the front caliper lines and don't forget you have another line to replace and that one is the one from the rear axle to the chassis.

In summary replace 3 flexible brake lines, flush the system then bleed and you will be good to go.
Don't try to shortcut and just replace one line, Replace all three it is well worth the effort.

Do this for my safety!! after all if you run on the road you don't want "Might stop Brakes" after all I am on the road too. :cool:
The Tek @ Large
Kent,Worshington
I was borne under a rock. So what's your excuse?

danboy282
Posts: 22
Joined: Sun Dec 25, 2011 5:13 pm
Location: Garden Valley, CA

Re: Brakes build too much pressure

Postby danboy282 » Sun May 06, 2012 9:05 am

Thats the second time I've heard that, so I'll give it a try today.

By the way I am in total agreement with you I want to be sure that when i hit the brakes those bad boy are gonna stop me. I like to bomb it, but not like that. :D

danboy282
Posts: 22
Joined: Sun Dec 25, 2011 5:13 pm
Location: Garden Valley, CA

Re: Brakes build too much pressure

Postby danboy282 » Mon May 07, 2012 3:44 pm

Replaced brake hoses with no luck

danboy282
Posts: 22
Joined: Sun Dec 25, 2011 5:13 pm
Location: Garden Valley, CA

Re: Brakes build too much pressure

Postby danboy282 » Mon May 07, 2012 11:51 pm

Both front caliper hoses replaced and problem still occurs. Gonna replace brake booster check valve and go from there.

Didn't do the check valve yet, but I rebuilt my calipers again to be sure they weren't sticking and the brakes ended up grabbing too much again.

Put in new rear wheel cylinders and still no luck.

I can't seem to locate a proportioning valve or a pressure differential valve.
Does my 86 B2 even have them? Where the hell is it located? Brakes are killin' me. :mad2:

drofman
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Location: san dirgo

Re: Brakes build too much pressure

Postby drofman » Tue May 08, 2012 6:01 pm

I'm thinking it might be the Master cyl. If the proportioning valve was stuck it should still bleed back though the Master and you would have no back brakes and may be an ABS light on. I hate to have you diag. with your wallet. I'm looking at my shop manual for brake drag, slow or incomplete release and it says:
Parking brake control or cables binding.
Brake pedal binding.
Front bearings out of adjustment.
Worn or damaged master cyl.
brakes out of adjustment.
restriction in hydraulic system (there you go Tek).
Seized wheel cyl. or caliper.
It doesn't say anything about a prop. valve

danboy282
Posts: 22
Joined: Sun Dec 25, 2011 5:13 pm
Location: Garden Valley, CA

Re: Brakes build too much pressure

Postby danboy282 » Tue May 08, 2012 6:59 pm

Thanks for the help. I think it may be the master cylinder too. Its about the only thing I haven't replaced new or taken apart and rebuilt myself. Either that or the rear brake hose isn't new.

they should make one of these little smilies holding a gun to it's head. boom

dgl6y6
Posts: 84
Joined: Wed Jul 22, 2009 8:56 am
Location: St. Louis

Re: Brakes build too much pressure

Postby dgl6y6 » Tue Jan 15, 2013 8:33 pm

it's not really a fix as it seems like there might be some other problem but just for the time being you can take off the master cylinder and turn the adjuster screw a couple turns in to put some more free play in the brake pedal, that may keep it from locking up on you while you're driving.

kirkland2887
Posts: 86
Joined: Sun Jan 29, 2012 6:00 pm
Location: Albion, Idaho

Re: Brakes build too much pressure

Postby kirkland2887 » Tue Jan 22, 2013 6:12 pm

When it happens, isolate the problem. put all four wheels in the air and see if just one is locking or multiple. this will narrow your search. if your proportioning valve is sticking, slamming on the brakes hard at about 10mph usually unsticks it. if all are locked up i would say master cylinder. if just front or rear, could be master cyl. or proportioning valve. If only one i would say line or caliper/wheel cylinder.


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