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brake bleeding problem/questions

Discussion in 'The Garage' started by madmike, Nov 13, 2002.

  1. madmike

    madmike 1/2 ton status

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    OK, here's what I have: /forums/images/graemlins/grin.gif'74 K10 with '85 D60 front and '77 Sub 14bff rear, stock brakes front and rear, all new pads, shoes, rotors and drums resurfaced, new calipers and wheel cylinders, new Skyjacker flexible lines, and a new master cylinder, p/n matches a '80 K20 (don't know why, maybe previous owner installed?).

    Before I started the axle swap, I had stock 1/2 ton running gear, the truck stopped well, even with 35" BFG Mud T/A's. Theoretically, the truck should stop very well now with all of the bigger brake stuff, and I'm only running LT235/85R16 tires. It's a good thing I don't have big tires on it or an automatic transmission, because I'm not sure I could stop it, the brakes don't work nearly as well as they should.

    Here's the problem: /forums/images/graemlins/confused.gifI have relatively low pedal height (yes, the rear brakes are adjusted), it feels spongy, and if I pump the pedal a few times, I get brakes. I think I just have air in the lines. I've tried bleeding the brakes three times. The master cylinder was bench bled before installing. I can hear the brakes expanding and contracting while pumping. Only one wheel, the right rear, seems to continually blow out air bubbles, the other three seem fine. It seems like the 1/2 quart of brake fluid I used just last night alone should have been enough to clear the air out of the lines.

    My questions are: /forums/images/graemlins/1zhelp.gif
    1. WTF?
    2. Could the one wheel cylinder be bad? I don't see any leaking though (anywhere)
    3. My friend checked the tightness of lines entering master cylinder, and put maybe a quarter turn on the one that feeds the front wheels. Could the mc have sucked in some air at this point, requiring me to re-bleed the mc?
    4. Is my mc (even though new) be bad?
    5. On the rear axle, where the little junction block sits, does that need to be level (just curiuos, I wouldn't think so)?
    6. Would having the brakes "power bled" solve my problem?
    7. WTF? /forums/images/graemlins/confused.gif

    I've never had a bad experience as far as bleeding brakes goes, but this is ridiculous, and its pissing me off, because the truck should stop better now than it ever did. It's mainly the RR wheel that seems to be the trouble spot. I'm just looking for answers/opinions on what the problem might be. Thanks men.
     
  2. K5er4Life

    K5er4Life 1/2 ton status

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    Most likely if you are running the factory proportioning valve it is not putting out enough fluid to stop the truck. I'm sure your brakes are fine, I have heard of this problem many times, probably if you do a search you can find someone with a similar problem. Answers to your questions are:1. WTF? hang on now Im only one man.
    2. Could the one wheel cylinder be bad? Possible but doubt it. 3. Could the mc have sucked in some air at this point, requiring me to re-bleed the mc? Dont think it could suck in any air at that point. 4. Is my mc (even though new) be bad? Anything is possible, but probably not. 5. On the rear axle, where the little junction block sits, does that need to be level (just curiuos, I wouldn't think so)? No.
    6. Would having the brakes "power bled" solve my problem? No.
    7. WTF? Try getting a Willwood adjustable proportioning valve and see if that helps at all, or you could eliminate the stock PV run the front right off the master cylinder(no PV) and install a after market PV to adjust the pressure to the rears. Hope this helps.
     
  3. milspecjimmy

    milspecjimmy 1/2 ton status

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    when you bleed the brakes, if the pedal hits the floor before you close the bleeder it can cause a problem like this, and you say the rear right has air comming out? did you start at the farthest wheel from the MC? and then work your way to the front? should go RR LR RF LF. i have always done it this way, and never had a problem. and i hear it makes a differance.
    /forums/images/graemlins/usaflag.gif /forums/images/graemlins/k5.gif /forums/images/graemlins/usaflag.gif
     
  4. madmike

    madmike 1/2 ton status

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    I bleed brakes same way, RR, LR, RF, LF. No, the pedal doesn't sink all the way to floor, allowing air in.

    Anybody else have any thoughts?
     
  5. txbluethunder

    txbluethunder 1/2 ton status

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    have you checked the vacuum assist coming from the intake manifold. maybe your not getting enough vaccuum to the booster?
     
  6. DieselDan

    DieselDan 1/2 ton status

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    My .02 The stock combination valve should (if anything) lock up the rear drums prematurely. The stock one ton trucks also run a load sensing valve under the bed -which you don't have(neither do I /forums/images/graemlins/wink.gif). I had a similar problem with mine after replacing a line. I bled and bled. Don't forget to push the button on the side of combo valve. I didn't have a working pressure bleeder at the time but it will definately help (the combo valve button must be held in during pressure bleeding).
     
  7. Klink K5

    Klink K5 1/2 ton status

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    I had a similar problem with pumping the pedal to get good brakes on a grain truck I once worked on. It was a f700 ford truck with a added tag axle. You had good brakes when your foot went to the floor,and really good brakes on the second stoke of the pedal. The priblem I found was that the master cylinder did not have the fluid capasity to provide enough brake fluid to all six wheels. I plugged the brake line to the tag and it had brakes right now! So the point I'm getting at, Maybe with all the added larger brake parts such as the dana front axle and the 14ff rear, your master cylinder doesn't produce enough brake fluid on the first stroke of your foot. May be you newed a larger master cylinder or a hydroboost set up! Hoped this helped. P.S. got the money order. Good luck, Klink /forums/images/graemlins/thumb.gif
     
  8. 77fixer

    77fixer 1/2 ton status

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    Please tell me more about this button on the side of the combo valve. I have never heard of this before and my brakes need help too.

    Brett /forums/images/graemlins/burb.gif
     
  9. madmike

    madmike 1/2 ton status

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    I'll look, but I don't recall seeing any "button" on the proportioning valve (same as 'combo' valve, right?). Does that button need to be held in during two-man bleeding, or just pushed in once? If I do take the truck somewhere and have it 'powerbled' do they need to hold the button in or just pushed once? Still don't remember seeing that button...I'll look tonight though. Thanks.
     
  10. madmike

    madmike 1/2 ton status

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    I've kind of thought about the fluid capacity deal too, but I believe there are guys on this site running 1/2 ton mc's with their one ton axles with no problems. Besides, my mc is a 3/4 ton one, which would match the rear 3/4 ton 14bff. My front brakes, even with the larger diameter/capacity calipers seem like they work fine, I just don't feel much braking action in the back, where the air seems to be. But, thanks anyway, and I'm glad you got the mo. Later!
     
  11. madmike

    madmike 1/2 ton status

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    /forums/images/graemlins/tongue.gifTTT /forums/images/graemlins/1zhelp.gif
     
  12. DieselDan

    DieselDan 1/2 ton status

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    The button on the combination (proportioning) valve is on the end under the rubber cap. I believe it pushes open the metering portion of the combo valve. Technically the metering valve holds pressure off the front brakes until 75-135psi it built up so the rear wheel cylinders can take up the slack. When pressure bleeding only 10+/-psi is pushed through the MC. So the button must be held on/open (there are tools to do just that). If you "two-man" bleed you shouldn't have to press it ('cause the MC build enough pressure to open it)but I've still had air bubbles in the system until we held the button on while bleeding. /forums/images/graemlins/grin.gif
     
  13. madmike

    madmike 1/2 ton status

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    OK DieselDan, sounds good. I am going to try to rebleed the brakes this weekend, and I'll look for the button. If I'm not successful in getting the air out of the lines, I may have to take it somewhere and have it pressure bled. The thought of that disturbs me, because I've never had to pay someone to work on my truck! Thanks for the help though!
     

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