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  • Brakes that don't release over drive time

    Hello all,

    I have a 77CJ. I converted from manual to power brakes. In the process of doing all this, I have replaced all kinds of parts to the tune of outragous$. My Jeep has disks up front and drums in the back. Currently, the brakes are "slightly" applied on startup. Meaning that it appears to me to have a extremely small amount of "brake" without pressing them. It seems harder than other vehicles I've worked on, to turn the wheels while on jack stands and no brake applied. You can't feel this driving at first, then progressively, with every stop the brakes get more and more firm...to the point that the disks get really hot in a five mile trip and you can feel the friction even on downhill slopes without pressing the brake. I have replaced everything I can think of and can't get this fixed? Any ideas are welcome. I have replaced:

    Master Cylinder
    Booster
    Vacuum lines-and tried other ports on manifold
    Proportioning valve
    Braided lines from steel on frame to caliper
    Calipers
    Steel lines from master cylinder to proportioning valve
    Disks
    Pads
    Thought heat from headers and reblead system wit DOT 4.

    I have brought this truck to dealers, friends and town mechanics with no luck? I can think of only one more thing to do that I will try this weekend. I had to make my own double flair lines from the master to the proportioning valve and my "loops" are not perfect.....came out more like circsquares (not kinked). Now that I have a "template" I will try fixing these. What are they for anyway?
    Thanks in advance!

  • #2
    I had that problem once with a dodge p/u. In that case the pads I bought were too thick (sounds crazy), the guy at the parts store said he had sold some like that before. bought a different brand and that fixed it.

    Also, is the little plunger that goes between the master cylinder and the brake pedal the same on manual and power brakes?

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    • #3
      I'll check that out...God knows I've been stuck with some bad parts from the locals in my town. The push rod is different and part of a kit I purchased from a very knowlegeble person in Mississippi. 4wd recommended him for parts they don't carry, Georges Jeep Parts. There is also an adjustment between the master and the booster. Which I have played with about 30 times with only about a 1/2 margin to adjust, which makes me feel like I would have hit magic by now. Also, I think that there is a hefty spring in the master that should push the piston to "nuetral" upon release as long as you have play at the top of your pedal, which I have. Thanks for the idea! I'll check into it.

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      • #4
        is the problem at all four corners or just up front or just one wheel? if it's just up front, then you likely have a problem with either the rear res in the master or one front the calipers aren't releasing due to them not being right, pads not being right or the fluid path is not clear. a tiny spec of dirt in the line will cause this. your foot pushes fluid past the obstruction, but the fluid will not then go back. had this very thing happen to the rear brakes on my truck. i thought it would "self adjust" after a few times hitting the pedal. got to work that morning and had smoke coming from my drums.

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        • #5
          The problem is equal on both front wheels. I have no rear brakes at the moment, which has progressively gotten worse trying to fix the front ones.

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          • #6
            Originally posted by gnarly
            I had to make my own double flair lines from the master to the proportioning valve and my "loops" are not perfect.....came out more like circsquares (not kinked). Now that I have a "template" I will try fixing these. What are they for anyway?
            Thanks in advance!
            The loops look like springs and that is exactly what they are for, as the body shifts on the frame (it always does, no matter what bushings you use) the distance from the master cylinder to the proportioning valve changes, they use the steel coils to allow for the shifting and it also helps cool the brake fluid a little bit.

            Did you put in a new or a used proportioning valve?

            was it adjustable?

            Did you use the special tool to hold the bleeder button on the valve while bleeding the brakes?

            Comment


            • #7
              New Proportioning valve, I did not notice any adjustment. It came from Inline Tube. The only difference from original that I noticed was the connector for the light on the dash. I did not use the tool...I have heard many schools of thought on that one. I started at the furthest wheel from the master and wentaround that way. Rear brakes are now working...it was the proportioning valve...it failed to the front when I replaced the calipers. A guy I talked to said sometimes you can free them by "smacking" the pedal really hard. It appearently works. Still got brakes that gradually apply over a period of three or four stops....Just can't figure it out.

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              • #8
                brakes when you don't need 'em...

                Stepping out on this one... I have a '77 CJ and have considered this same modification...

                It sounds like your 'vacuum assist' has no way to relieve itself. Each time you apply the brakes you add to the trouble of relief. I don't have the technical knowledge to tell you where to check but I DO know that whatever pressure is being applied to your brakes is not being 'unapplied' when you release pressure on the pedal. (If this sounds 'obvious' I apologize. However, I have noticed that often it is the obvious that plagues us.)

                Would you send me a personal message with regard to what you have done so far with your mod? My CJ scares me sometimes with its cavalier attitude toward stopping no matter what pops up in front of me. thx, blackwater

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