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Help with brakes

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by outlaw612, Sep 28, 2001.

  1. outlaw612

    outlaw612 1/2 ton status

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    I finished my axle swap/lift install/rear disc conversion today. All thats left is to mount the TSL's and install the stabilizers. 1 problem. I cant get the brakes to get any pedal pressure. If I push the pedal all the way to the floor I cant turn the rear wheels by hand, but its nowhere near strong enough. When you pump up the brakes and open the front bleeder, you can feel the pedal drop, but when you do the same to the rear, cant feel the pedal move. Ive been through 2 32ounce bottles of fluid bleeding them. Please HELP!!!

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  2. scrapmetal

    scrapmetal 1/2 ton status

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    Well I have had that happen to a freind and once to me, and they were both two different things, 1 did you make sure there are new wheel cylinders in it, 2 is the proportioning valve working, and 3 if you put in a 14ff and a 60 your gonna need a 1-ton master cylinder to run those brakes, Im sure there are people who run the half ton models on theres and have no problems, but there asking for it, pull the drum off the rear and have someone step on the brakes, if the wheel cylinder moves then your bleeder valve is messed up, if the wheel cylinders dont move crack a line on the proportioning valve to the rear and step on the brake again, if its leaking from there then its one or the other, process of elimination. also does your master show any signs of leaking, or is it old and maybe having a problem pumping those mongo brakes,, thats about all I can think of, its gotta be one of those,, if not then maybe a loose nut behind the wheel,,

    Never been stuck, just temporarily delayed.
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  3. thebigdaddyof2

    thebigdaddyof2 1/2 ton status

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    My buddy just went through this same $hit. One question, did you let the rear line drip (until dry) while you were changing out the rear axle? That is what he did and could never get enough pedal- always went to the floor. He tried everything including gravity bleeding, power bleeding and a rebuilt A/Z master cylinder. No change. He tried another rebuilt A/Z master cylinder. No change. On my advice, he tried a new master cylinder from a real part store and would you guess....it worked. Something strange happens when you let a master cylinder go dry- like the piston gets bound up or something. Good luck though.

    thebigdaddyof2
     
  4. outlaw612

    outlaw612 1/2 ton status

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    It has rear disc so the wheel cylinder idea isnt gonna work. The mastercylinder is about 6-8 months old, all 4 calipers and rotors are new. Will a 1 ton MC bolt in place of the 1/2 ton unit?

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  5. outlaw612

    outlaw612 1/2 ton status

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    The entire rear brake line was replaced from just before where the rubber line bolted on and all across the rear axle with braided stainless line. Is it worth buying the 1 ton MC if I have to buy a new one?

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  6. scrapmetal

    scrapmetal 1/2 ton status

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    Well even if it has discs, you should stil be able to see the disc pads move, and yes the 1-ton mc bolts up the same, I have one on my Blazer, I used the half ton one for a couple days, then I noticed I started to get brake fade, so I went up to the bigger one. If you pads dont move then could be the proportioning valve, I have had one go bad on me, except mine locked up one of my tires on the interstate at 70, makes for alot of smoke, had to disconnect the right front and limp home with three brakes. Are you getting any fluid out of the calipers when you bleed them? If so then Im stumped,, anybody esle???

    Never been stuck, just temporarily delayed.
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  7. scrapmetal

    scrapmetal 1/2 ton status

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    master cylinders dont suddenly go bad by dripping dry, you have to re prime them and bleed out the air, just like you do with one you get brand new, they all half to be bench bled,

    Never been stuck, just temporarily delayed.
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  8. thebigdaddyof2

    thebigdaddyof2 1/2 ton status

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    Ah yes, bench bleeding a master cylinder. That's something I'll have to try in the future.
    Thanks so much for the info!

    thebigdaddyof2
     
  9. outlaw612

    outlaw612 1/2 ton status

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    Yes, Im getting fluid out of all 4 bleeders, but it doesnt shoot out of the rear like it does on the front. I cant see any air coming out of them anymore either. Im gonna get a 1 ton MC, couldnt hurt to have a bigger one anyways. Is the proportioning valve the piece all the lines go into on the front crossmember?(Below the radiator?) My bleeders arent at the 12o'clock position, but they are above where the lines bolt on. Could this be a problem?

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  10. chevrules

    chevrules 1/2 ton status

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    I did the same swap on my '87.I used an adjustable proportioning valve to the rear.I put it inline to the rear brakes,it has a dial and you can adjust the pressure to the rear...worked great.This is common with rear disc conversions,I have used the adjustable valve on my last 2 trucks.Just my 2 cents.

    chevrules...always has and always will
     
  11. COOTER

    COOTER Registered Member

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    YOUR PROPORTIONING VALVE SHOULD BE MOUNTED ON THE FIREWALL NEAR OR UNDER THE MASTER CYLINDER.
     
  12. outlaw612

    outlaw612 1/2 ton status

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    Thanks for all the help, Im gonna replace the MC and change to an adjustable proportioning valve and see how that works.

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  13. outlaw612

    outlaw612 1/2 ton status

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    Can I do away with the whole factory proportioning valve and just run 2 aftermarket valves? (one for the front and one for the rear?) If so, how much pressure should be going to the front/rear?

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  14. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

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    make sure the bleed screws arnt plugged ... duh ... .02. and yes the prop valve is under the radiator and there is a lil button on the left end that is sposed to be held whilest you bleed the brakes , its says that in my chiltons manual , i never have done it but it may help ... good luck

    WHATS WRONG WITH A 305 ?
    81 K10 GOODYEAR 35" MTRS
    TH350 NP 208
    STEPHENS OLD AXLES
    NO BREAKAGE :)
     
  15. taterblazer

    taterblazer 1/2 ton status

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    Make sure you don't have the rubber seal on the brake fluid resevoir on. Mine was creating serious back presure. Pulled it off and walla a bleading we went.
     

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