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No Brakes!

Discussion in 'Intermediate CJ-5/6/7/8' started by brianmurphy, Aug 3, 2015.

  1. Aug 3, 2015
    brianmurphy

    brianmurphy 866

    Whitmell, Va.
    Joined:
    Jan 4, 2007
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    38
    Taking a spin on the jeep Saturday when I get to the stop sign at the end of my road and NO BRAKES! Pump pump pump NO BRAKES! Luckily there was nothing coming when I blew the stop sign. There is only slight braking power and no amount of pumping the pedal will increase it. Back home I removed the master cylinder cover and the rear reservoir is empty. There is no sign of leaking at the brake backing plates that would lead me to believe that I have a blown wheel cylinder ('73 drum brakes all around). No leaking around the MC. So before replacing the MC I'm going to try cleaning up the MC, replace brake fluid and give the brakes a thourough bleeding. Should I remove the MC and bench bleed it too? Should I just go ahead and replace the MC before investing a bunch of time on a defective one. It apears to be a reman unit anyway. Are the master cylinder rebuild kits a practical solution? And finally, with the front reservoir full but only slight braking power does this mean that my front brakes aren't up to snuff? I read somewhere once that 80% of your stopping power should come from your front brakes. Any input will be appreciated.
     
    Last edited: Aug 3, 2015
  2. Aug 3, 2015
    Chilly

    Chilly Active Member

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    73 should have a brass valve body on left frame rail where all brake lines come together. If a front or rear circuit blows a line a sliding valve should isolate the leak and send fluid only to the intact circuit. A switch will activate a brake warning Leigh on speedo cluster. My FSM says this function came standard with Wagoneer and truck models, and as available on CJ models. My 73 is so equipped.

    I'd say your master cylinder is leaking by if you don't see any leak sources elsewhere. Is your firewall peeling paint? Steering shaft? Clutch bell crank wet? I rebuilt my MC because reman units looked like junk. Shot blasted, including fitting threads. Barely any threads left. Sealing cone rough as a cob.

    Chilly
     
  3. Aug 4, 2015
    nickmil

    nickmil In mothballs.

    Happy Valley, OR
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    I would put in fluid, bleed, and track down the source of the leak rather than arbitrarily replacing parts.
     
  4. Aug 5, 2015
    brianmurphy

    brianmurphy 866

    Whitmell, Va.
    Joined:
    Jan 4, 2007
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    Good advise. Thank you gentlemen. I added brake fluid and pumped the brake pedal ONE TIME and had brakes again. But stiil time for some brake maintenance. I'll try to score a brake bleeder tool this WE and change the fluid and keep an eye on that MC and check the brake liners. My dad always called them "binders". I've owned this CJ5 for ten years and the other day was the first time I've ever removed the MC cover.
     
  5. Aug 5, 2015
    Chilly

    Chilly Active Member

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    Friend has a 66 Charger. Never sees a leak but regularly needs to add fluid. Old vehicles can have slow weeps that leave little sign leaks. 10 yr is a long time to not pull a cover that doesn't even require a wrench. I might suggest checking differential lube, tranny, and transfer case levels. Re packed front wheel bearings lately? Pump some grease in ball joints, steering links, u-joints?
     
  6. Aug 5, 2015
    timo2

    timo2 Member

    SE by NW
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    Apr 2, 2015
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    Didn't see whether you have PB booster, but sometimes it can draw fluid out out o the MC, under vacuum, very quickly.

    I agree, ten years is way too long without checking brake fluid. It absorbs moisture from the air, evaporates, leaks/seeps, as well the fluid goes down as the frictions and drums/discs wear...
     
  7. Aug 6, 2015
    brianmurphy

    brianmurphy 866

    Whitmell, Va.
    Joined:
    Jan 4, 2007
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    38
    It's a JEEP! Dont need no sissy lubricants! No, seriously I've changed all (of the other) fluids. I've always thought that my brakes performed pretty well for a +40 year old vehicle and have been afraid to mess with them. Been more focused on the steering lately.
     
  8. Aug 8, 2015
    OleBlue

    OleBlue Sponsor

    Tennessee
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    Is this brass valve body you speak of only on the rare factory power brake option? My factory manual brake setup has a brass tee at the location you describe and it is only there for teeing off the lines going to the front wheel cylinders.
     
  9. Aug 8, 2015
    timgr

    timgr We stand on the shoulders of giants. 2022 Sponsor

    Medford Mass USA
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    The combination valve would be used regardless of manual or power brakes. On drum brake CJs, they housed the brake warning light switch, and a valve to hold off rear brakes during severe braking. This would prevent rear-wheel lockup during emergency stops. You can look at the '74 TSM http://oljeep.com/gw/74_tsm/9-BrakesWheels.pdf P. 9-19 and see the valve.

    I expect that 1972 and 1973 CJs were not equipped with with combination valves, The '72 TSM makes no mention of them, and i do not recall one being there on my '73 CJ-5 long ago. I do not have a '73 Jeep or TSM to refer to, but if they were used, they should be present there. Certainly they were present (again) in 1974 and 1975.
     
    Last edited: Aug 8, 2015
  10. Aug 8, 2015
    OleBlue

    OleBlue Sponsor

    Tennessee
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    Mine is a 73, hence no valve.
     
  11. Aug 8, 2015
    Chilly

    Chilly Active Member

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    My 73 has a valve that isolates a leaking circuit and includes a switch to activate the warning light. I think the valve that also delays rear brake action came in 74 base on Tim having one. My 73 manual makes no mention of the rear brake delay function.

    The brass block for the switch an safety valve has a nylon connector for switch harness. If you have just a simple brass 4-way fitting the correct piece has been removed. If available its worth having in case you break a line on a stump or something.
     
  12. Aug 8, 2015
    timo2

    timo2 Member

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    I have a '73 which appears to have a valve. I suspect adding one is a good idea...
     
  13. Aug 9, 2015
    Chilly

    Chilly Active Member

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    Boy was I ever wrong! I'm installing freeze plugs in the Jeep and noticed my Jeep (1973, June I think) does NOT have the valve. I was recalling a 1974 CJ5 that I tore apart 20 years ago! My 73 has dual reservoir MC so the valve would not be needed. Front circuit spits from a T on top of the frame just above the axle.

    Funny how old memories displace new facts. I think that's a symptom of some age-related memory thing, but I don't remember what it's called.

    Where am I?
     
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