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Brake Problem Solved

Discussion in 'Intermediate CJ-5/6/7/8' started by Dphillip, Mar 8, 2010.

  1. Mar 8, 2010
    Dphillip

    Dphillip Sponsor Sponsor

    Omaha NE
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    After swapping axles on my CJ-7 (D44 front, Ford 9" rear) I could never seem to balance the vacum assist brake system. When I used the factory proportioning valve the front disc's would work great but the rears would hardly apply. I installed a new proportioning valve and the opposite happened. Rears would lock up and fronts wouldn't apply. I then tried an adjustable proportioning valve to reduce pressure to the rear brakes. Even after installing the adjustable valve the front brakes hardly applied. I had no idea what was going on. Totally confused, I removed the proportioning valve completly and just ran straight lines directly from the Wagoneer master cylinder to the front and rear brakes. I maintained the adjustable proportioning valve and also added a 10 pound residue valve to the rear brakes. PERFECT! The brakes have never worked better.

    In reading this forum it appears that brake bias is a common issue. IMO proportioning valves are now highly over rated.
     
  2. Mar 8, 2010
    dnb5853

    dnb5853 Member Sponsor 2019 Sponsor

    SLC, UT
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    Do you have drums on the rear?
    A 10 lb residual valve seems high for disks.
     
  3. Mar 8, 2010
    nickmil

    nickmil In mothballs. Sponsor

    Happy Valley, OR
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    I think you must mean the metering valve. Proportioning valves simply control how much pressure is allowed to the wheel cylinders in a drum brake system. You already stated you kept the adjustable unit in yours. If you don't have one in the drum brake system on a disc/drum system you chance the drums locking up before the discs start operating. A metering valve holds off pressure to the discs until enough pressure builds up in the drum brake system. This keeps the fronts from operating too soon, i.e. before the rears can start working. This keeps proper balance in dissimilar brake types (drums vs. discs). If this valve is not installed, on some systems, the discs could lock up at slow speeds on slippery surfaces before the rear brakes even start applying due to the distance the shoes must travel before they contact the drums. Disc brakes are much quicker to apply.
    Sounds like you had a couple of combination valves that were not working correctly.
    Not all vehicles use metering valves but most modern vehicles do for safety reasons stated above.

    Proportioning valves are not over-rated. If so why did you keep the adjustable one in your system?

    Remember, you changed and modified the brake system. The parts don't know the difference and didn't mix and match themselves.

    Glad you got your system working ok.
     
  4. Mar 8, 2010
    Dphillip

    Dphillip Sponsor Sponsor

    Omaha NE
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    I do have drums brakes in the rear and all my research indicated a 10 pound residue valve was proper for the rear brakes.

    I refer to it as a proportioning valve because everyone that I know calls the large brass fitting with brake lines going in and out a proportioning valve. If you Google "Jeep proportioning valve" you'll see pictures of it.

    Apparently my parts did know the difference because they didn't work propertly until I removed the valve.
     
  5. Mar 8, 2010
    nickmil

    nickmil In mothballs. Sponsor

    Happy Valley, OR
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    Dphillip, I wasn't trying to be mean or anything like that. I was just simply trying to educate you on what the parts are, what they are called, and what they do. Sorry if it came across wrong.

    A 10lb. proportioning valve is just about right for drum brakes.

    A combination valve has a proportioning valve and metering valve, a pressure differential switch and proportioning valve, a pressure differential switch and metering valve, or a combination of all three. Hence the name combination valve. A proportioning valve only reduces pressure to the brakes to keep them from locking up. Generally used in the rear on drum brakes as on a rear wheel drive vehicle the rear is lighter and the braking is split about 60% braking in the front and about 40% in the rear.


    Again, it sounds like your metering valve was not working correctly and you got one that was defective as well. Again, not all disc/drum brake systems need them or used them.

    Everyone around here calls adjustable wrenches Crescent wrenches but that don't make it correct;) Just cause that's what's on Google don't make it gospel;):beer:

    Again, glad you got it working ok.
     
  6. Mar 8, 2010
    Patrick

    Patrick Super Moderator Staff Member Sponsor

    Los Alamos, NM
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    Channel Locks, anyone? :D
     
  7. Mar 9, 2010
    dnb5853

    dnb5853 Member Sponsor 2019 Sponsor

    SLC, UT
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    Those would be adjustable joint pliers (technically). :rofl:
     
  8. Mar 9, 2010
    Posimoto

    Posimoto Hopeless JEEP Addict Sponsor

    Minden, Nevada
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    Actually, slip-joint pliers. ;)
     
  9. Mar 10, 2010
    dnb5853

    dnb5853 Member Sponsor 2019 Sponsor

    SLC, UT
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