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Thread: brake bleeding questions

  1. #1
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    Default brake bleeding questions

    well as you all know my cj does not run.. .:wavzing:

    i need to bleed the brakes (let me rephrase that.. everything is empty and i need to get the brakes to work).

    it is a 80 cj5 with a yj master/ booster, widetracks out of a 86 cj. and all new s.s. prebent brake lines and skyjacker braided.

    anyway once i fire up the jeep i would like to take it for a little spin around the street to see what bugs need addressed. i would prefer to have brakes before i start the jeep up.

    can i bleed the brakes (with power booster) effectivly without special tools and having the jeep running?

    should i not bother or just wait till i get the jeep running?


    coming down to the wire now!
    body off 80 cj5
    resto started 10-31-04
    360, t-176, d300
    86 CJ widetrack axles
    2.73 gears with d44 rear
    33-10.5 bfg at's
    j-20 steer box
    warn 8274
    JKS disco's
    alcan custom 3.5" rear & 4" front springs
    howell C.A.R.B approved 50 state legal T.B.I

    in the process of final assembly now.

  2. #2

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    No need for it to be running. In fact, it is better if it isn't. Do bench bleed the MC first, before attempting to bleed the system.

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    Registered CJinPA's Avatar
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    Be sure to hold the pin out on the front of the proportioning valve when you bleed the system. A pair of vise grip pliers will work.
    84 CJ7 Northstar 4.6L V8.
    91 YJ Renegade
    97 TJ

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    yeah i need to do that.. i dont know how much help it will be since EVERYTHING is empty.. i wonder if those pressure bleeder things would work well for me, maybe i can rent one?
    body off 80 cj5
    resto started 10-31-04
    360, t-176, d300
    86 CJ widetrack axles
    2.73 gears with d44 rear
    33-10.5 bfg at's
    j-20 steer box
    warn 8274
    JKS disco's
    alcan custom 3.5" rear & 4" front springs
    howell C.A.R.B approved 50 state legal T.B.I

    in the process of final assembly now.

  5. #5
    Registered CJinPA's Avatar
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    I would go buy some speed bleeders. Then you can bleed the system yourself without having someone else to pump the brakes.
    84 CJ7 Northstar 4.6L V8.
    91 YJ Renegade
    97 TJ

  6. #6

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    Pressure bleeding works well, as does vacuum bleeding. Speed Bleeders are a good little device, as well.
    I wouldn't want to rent a pressure bleeder.. Too much chance of contaminant from some previous user. There are relatively inexpensive plastic pressure bleeders on the market, now. I've never used one of them, but as long as they're well designed, they should be OK. (Try a google search to find them.)

  7. #7
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    Quote Originally Posted by CJinPA
    Then you can bleed the system yourself without having someone else to pump the brakes.
    This is easy without the speed bleeders. Run a hose from the bleeder screw and down into a jar/bottle of brake fluid. The end of the hose must remain submerged. Pump the brakes until you see no more air bubbles coming out of the hose.

    With the end of the hose submerged air can not be introduced back into the system as you release the pedal.

  8. #8

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    Quote Originally Posted by Snowtow
    This is easy without the speed bleeders. Run a hose from the bleeder screw and down into a jar/bottle of brake fluid. The end of the hose must remain submerged. Pump the brakes until you see no more air bubbles coming out of the hose.

    With the end of the hose submerged air can not be introduced back into the system as you release the pedal.
    This is a relatively effective system, although some air can bleed in around the threads of the bleeder screw. The speed bleeders exclude the air from the threads w/ some sort of thread locker-like material. This is probably their biggest asset (and something that could probably also be accomplished w/ a bit of judiciously placed teflon tape.... although it would have to be placed in such a manner that there was no possibility of a bit of material entering the system.

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    Registered CJ-8_Jim's Avatar
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    Quote Originally Posted by CJinPA
    Be sure to hold the pin out on the front of the proportioning valve when you bleed the system. A pair of vise grip pliers will work.
    Not sure if that's required on YJ combination valves (sometimes mistakenly called proportioning valves because it contains both proportioning and metering functionality in one unit) and if it is, I'm not sure if YJ metering pins should be pulled or pressed.

    HOWEVER, on 80's CJs the combination valves, the metering pin should be DEPRESSED... not pulled when bleeding.

    Straight copy/paste from the YJ manual, here are brake bleeding instructions:

    Quote Originally Posted by YJ Repair Manual
    Bleeding Brake System
    Jeep Wrangler/YJ 1987-1995 Repair Guide

    Vehicles equipped with an Anti-lock Brake System (ABS) require a special bleeding procedure. Please refer to ABS Bleeding, later in this section. [/I]
    The hydraulic brake system must be bled whenever a fluid line has been disconnected because air gets into the system. A leak in the system may sometimes be indicated by a spongy brake pedal. Air trapped in the system is compressible and does not permit the pressure applied to the brake pedal to be transmitted solidly through the brakes. The system must be absolutely free from air at all times. If the master cylinder has been overhauled or a new cylinder has been installed, bleed the cylinder on a bench before installation. When bleeding brakes, bleed at the wheel most distant from the master cylinder first, the next most distant second, and so on. During the bleeding operation the master cylinder must be kept at least 3/4 full of brake fluid.

    Bleed the brake system in the following sequence:

    Master cylinder

    Right rear wheel

    Left rear wheel

    Right front wheel

    Left front wheel

    To bleed the brakes, first carefully clean all dirt from around the master cylinder filler cap. Remove the filler cap and fill the master cylinder with DOT 3 brake fluid to the lower edge of the filler neck.

    Bleed the master cylinder first. Have a helper operate the brake pedal while bleeding each master cylinder fluid outlet line. Do not allow the master cylinder to to run out of fluid,as this will allow additional air to be drawn into the cylinder.

    Clean off the bleeder connections at all four wheel cylinders. Attach the bleeder hose to the right rear wheel cylinder bleeder screw and place the end of the tube in a glass jar, submerged in brake fluid. Open the bleeder valve 1/2-3/4 of a turn. Have an assistant depress the brake pedal slowly and allow it to return. Continue this pumping action to force any air out of the system. When bubbles cease to appear at the end of the bleeder hose, close the bleeder valve and remove the hose.

    Check the level of fluid in the master cylinder reservoir and replenish as necessary.

    After the bleeding operation at each wheel cylinder has been completed, fill the master cylinder reservoir and replace the filler plug.

    Do not reuse the fluid which has been removed from the lines through the bleeding process because it contains air bubbles and dirt..
    1985 CJ-8 Laredo
    Becoming a little less stock (4.0 HO head, MPI, D44 rear, stereo)

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    Quote Originally Posted by CJ-8_Jim

    HOWEVER, on 80's CJs the combination valves, the metering pin should be DEPRESSED... not pulled when bleeding.
    That is not always true. There were two p-valves used on the jeeps. One is rounded edges and the other is square edged. If I remember correctly, the square is pulled, the rounded is pushed.

  11. #11
    muchacho largo longboy's Avatar
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    Is this metering pin to be pushed/pulled whenever bleeding any brake line? Or just when doing the fronts, or just the rears...or?

    The reason I ask, is I just swapped in a different front end and bled the brakes. No bubbles...but it's a tad mushy on the first push. Pump 'em a 2nd time and they're fine. I'm thinking that the combo valve button thingy is my problem, as I didn't do squat with that.

    I'll have a looky at my FSM when I get a chance and see what's up. Thanks for the info on this-
    2006 WK 5.7 Hemi

  12. #12
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    Quote Originally Posted by Snowtow
    This is easy without the speed bleeders. Run a hose from the bleeder screw and down into a jar/bottle of brake fluid. The end of the hose must remain submerged. Pump the brakes until you see no more air bubbles coming out of the hose.

    With the end of the hose submerged air can not be introduced back into the system as you release the pedal.
    Works okay as long as you've got someone to assist you, otherwise it's kind of a bitch for one person to simultaneously pump the brake pedal and observe the hose on the right rear brake.

    I've long preferred to use a MityVac hand vacuum pump to bleed hydraulic brake and clutch systems.
    1982 Jeep CJ-8 Scrambler.

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    Quote Originally Posted by CJ5_Fan
    That is not always true. There were two p-valves used on the jeeps. One is rounded edges and the other is square edged. If I remember correctly, the square is pulled, the rounded is pushed.
    If the COMBINATION valve looks like this (80s CJs), then you want to push the metering pin on the end.
    The FSM is quite clear and the tool only allows for it to be pushed.

    NOTE: Chiltons & Haynes manuals are incorrect when they advise to pull the metering pin.

    Pretty important to get this correct since only half your brake system will work otherwise.
    Attached Images Attached Images
    1985 CJ-8 Laredo
    Becoming a little less stock (4.0 HO head, MPI, D44 rear, stereo)

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    Quote Originally Posted by CJ-8_Jim
    Chiltons & Haynes manuals are incorrect when they advise to pull the metering pin.
    I was not aware of that. Both my manuals say that the square edge (type W) is to be pulled out. Anyway you can verify that the FSM is refering to the type W valve used in the 79-86 models and not the previous version (77-78) which was pushed in?

  15. #15
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    Quote Originally Posted by longboy
    Is this metering pin to be pushed/pulled whenever bleeding any brake line? Or just when doing the fronts, or just the rears...or?

    The reason I ask, is I just swapped in a different front end and bled the brakes. No bubbles...but it's a tad mushy on the first push. Pump 'em a 2nd time and they're fine. I'm thinking that the combo valve button thingy is my problem, as I didn't do squat with that.

    I'll have a looky at my FSM when I get a chance and see what's up. Thanks for the info on this-
    From one of my earlier posts on a different thread of the same subject....

    The metering pin is set when bleeding the rear brakes. The metering pin on the stock, brass CJ combination valve (see photo in my post above) prevents the "front brakes from locking before the rear shoes have a chance to activate. It functions by delaying fluid pressure to the front brakes [until a specified pressure level in the system]. Since the rear cylinders require more fluid travel to push the shoes out against the drums than the discs do (as well as overcome the return spring pressure), the valve will in effect balance and equalize the pressure applied to all four brakes."

    The metering pressure is predetermined by design. If you changed calipers when you swapped in a different front end, it's quite possible you need a different metering pressure calibrated for whatever front calipers and rear calipers or drums you are using.

    You could:
    a) try to find the correct combination valve for the brake system you have, OR,
    b) install separate aftermarket metering valve and proportioning valve (a combination valve incorporates both functionality) that are spec to the brakes you are using (it's common for hot rodders to go this route).
    1985 CJ-8 Laredo
    Becoming a little less stock (4.0 HO head, MPI, D44 rear, stereo)

  16. #16
    muchacho largo longboy's Avatar
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    Quote Originally Posted by CJ-8_Jim
    The metering pressure is predetermined by design. If you changed calipers when you swapped in a different front end, it's quite possible you need a different metering pressure calibrated for whatever front calipers and rear calipers or drums you are using.
    I didn't change calipers in respect to size. I swapped a D30 for a D30, same calipers, etc.

    Also, still running factory size/spec rear drums as well on an AMC 20.

    I'm thinking I just need to rebleed and doublecheck that I got all the air out. I'll do some searching on the other brake threads. Thanks!
    2006 WK 5.7 Hemi

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    Quote Originally Posted by CJ5_Fan
    I was not aware of that. Both my manuals say that the square edge (type W) is to be pulled out. Anyway you can verify that the FSM is refering to the type W valve used in the 79-86 models and not the previous version (77-78) which was pushed in?
    My 1985 FSM (factory service manual) is quite clear that the squared edge (type W) pictured above should be pushed in. I've only seen Type W on stock 80s CJs.

    Chiltons & Haynes try to cover so many model years that occassionally they get it wrong/make it unclear.
    1985 CJ-8 Laredo
    Becoming a little less stock (4.0 HO head, MPI, D44 rear, stereo)

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    So what actually is the purpose of pushing/pulling the pin as the case may be? I've been trying to find this out ever since we've had the Jeep. Seems like you should be able to bleed the brakes without fooling with it. After all, the pin isn't held in or out during normal operation, and the brake fluid is still getting pushed back to the rear brakes. Seems like as long as brake fluid is being pushed back there, it would push the air out.

  19. #19
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    I swapped in a brake booster and master cylinder from a 95 YJ a few weeks ago and thus had to bleed the system on my 84 CJ. I tried to bleed it without messing with the p-valve ( one pictured above) and the brake pedal would not firm up. So I did what the Haynes manual says and held the pin OUT on the p-valve and bleed the system. The remainder of the air was pushed out of the lines and the brake pedal is now firm.
    84 CJ7 Northstar 4.6L V8.
    91 YJ Renegade
    97 TJ

  20. #20
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    I could never get the pin to pull out or push in, so we always bled with it in the normal position and never had any problem with the brakes.

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