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73-87 Chevy _ GMC Trucks => Brakes, Frame, Steering & Suspension => Brakes and Braking Systems => Topic started by: #1 Kawboy on November 17, 2014, 10:10:51 am
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Hi all !! New to the group ! Sooooo......My 87 454, auto, Crew cab Dually has a problem I can't seem to chase down. One day at the boat ramp, the power steering quit, brakes got hard. Brake pedal SLOWLY comes back after braking. Pedal goes farther down than it should upon braking but stops the truck. Upon initial braking, pedal has a slight 'bucking' to it. Replaced power steering pump and hydro boost unit with GM parts, Master cylinder from NAPA, and had both high pressure lines tested both ways ( and are fine ) power steering works fine now. Brakes work just not letting pedal return. Have to pull it up with toe. Things I've checked....rod in hydro boost is correct, spring under dash is fine, pedal movement not restricted by wires etc. Who's a pro at this ?!?! Need help !
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::)If possible pump the pedal fast pushing down in 1" increments (need 2 people) while doing this have the cap off the reservoir and watch the front for flowing fluid. Master cylinder you got may be defective.
and did you remove air pockets when u replaced power steering setup?
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The only way I know (knew ) how to "bleed" air pockets was to jack up front, turn to left / right with motor off, then running.... How do you do it ?? Could be the problem ? Will check m/c tonight.
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I'm sure there is more technical ways to do it but that is how I do it as well, when you turn it lock to lock are you holding it slightly at lock? Usually you can take cap of power steering pump and look in as you do this to see if there are pockets coming out or not
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Well....I've done that a lot....never looked in before. Funny thing is now, with motor running, when hit the lock in either direction, the brake pedals gets depressed about an inch or so, all by itself.
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Does the pedal come back up when you turn back out of full lock?
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Yes.
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New master cylinder / brake bleed....still won't come up quickly :( ??? ANYBODY HELP ??
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Probably did this but you do have enough fluid right?
So when you depress the brake is comes up slow or not at all now?
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do your brakes release when you release the brakes or do you have to lift the pedal up for them to release?
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Fluids are fine. Both systems ( brake/ m.c/ lines and pow. st. ) bled. Brakes work. Release fine, I put it on stands and checked all 4 corners. When I first hit the pedal, there is a grab, then it smooths out as pedal goes down. Pedals comes up to rubber stop in about 15-20 seconds, and still doesn't FULLY come up. Last 1/2 inch or so has to be pulled up with toe. Everything seems to work OK ( I haven't tried stopping with a load on it yet, kinda scared...) at 45 mph, it lock all 6 wheels up and STOP. Just the initial GRAB, and sloooooow pedal driving me nuts !!! I also found there were two lengths of push rod in the Hydro boost, mine is the longer of the two, which according to my brake code in the glove box is correct, as well as the hydrboost. All parts NEW from GM dealership, not Chinese junk....
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Hmmmmm....guess everyone's as stumped as I am ??? 227 views and no answers :-[...
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Have you pulled it back off and made sure the spring in the hydroboost is not broken?
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Several times......it's new as well
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when you replaced the master cylinder, booster and power steering who did it? did they all get replaced at the same time? i wonder if the master cylinder could be bad even with it being new or if it wasnt done right?
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I have eliminated that issue. ALL 3 PARTS, have been replaced 3 times !!! I'm pretty dang sure, it's not a " bad part." Replaced one at a time, all 3, at the same time, and all 3 again.........
GM stuff.....
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the only thing left is the load sensing proportioning valve and the proportioning valve or air in the system
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did you ever figure it out?