Brake Booster Question

Discussion in '40- & 55-Series Tech' started by cruiserjunktion, Jun 14, 2005.

  1. cruiserjunktion

    cruiserjunktion Cruiserjunktion@gmail.com Supporting Vendor GOLD Star

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    I installed a 84 P/U m.c. & a JTO front disc brake kit. I am having trouble bleeding the brakes. I bled the m/c on the booster. I am using the "gravity method" from the caliper's breathers to bled the front brakes. I have done this several times (8). The new calipers still won't budge. The brake pedal comes back after pushing it, and fluid is getting to the calipers.


    I do hear a hiss from the carb when the pedal is being pushed.
    Why does air come out of my carb when the brake pedal is pressed? I have only heard it with the air cleaner and engine off and someone else pressing the pedal.
     
    Last edited: Jun 14, 2005
  2. dustin

    dustin

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    did you bench bleed your mc? or is that what you meant by "I bled the m/c on the booster"? Probably has an air pocket in it. Or, there is a check valve in it that is malfunctioning.

    What booster are you running? Your booster wont (atleast I dont think it will) make your brakes not bleed. It could make your pedal really stiff though if its not working right, like a blown diaphram.

    -Dustin
     
  3. TonkaC

    TonkaC

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    I tried a MC around that year and it wouldn't work correctly for me. I spent a little extra and got a '95 TLC MC. It is setup for 4 wheel disks and works great.

    If your MC sits level in the vehicle, I've never had to bench bleed them. The ones that sit with an up angle can get air caught in the tip of them where it is higher than the front resevoir hole into the MC.

    NOTE: If you return the core of your old MC after you pick up the new one they never notice that it is different than the original one.
     
  4. Ian Rogers

    Ian Rogers

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    Are you running a booster?
     
  5. tornadoalleycruiser

    tornadoalleycruiser SILVER Star

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    I'll try here..
    You "gravity Bled" does that mean you just cracked the bleeders below and waited? or did you follow the proper description in a car manual and had someone pump the brakes and you opened and shut the bleeder? Or used a hose submersed in Brake fluid and waited till there were no bubbles? Use a mityvac?
    You are running an 84 PU master cylinder? I'm guessing that's 7/8 or smaller? What's stamped on the side? THE JTO whatever brakes are what? MonteCarlo calipers? Which is probably taking much more fluid flow than your stock drums? I'm assuming your talking about an FJ40?
    What year? did it orginally come with a booster?
    Have you checked your booster via the FSM test procedure? Starting the vehicle, pushing the pedal, shutting it off etc?
    Have you replaced any of the soft lines on the brake system? those rot inside and can flex causing a loss of pressure.

    We need?
    Size of Master cylinder?
    Year, if it came with a booster?
    Type of caliper used?
    Have or have not replaced flex lines
    Bled properly?
    tested booster?

    If it didn't come originally with a booster there is a difference in the throw on the pedal which will affect performance when a booster is added.
    MORE INFO PLEASE
     
  6. cruiserjunktion

    cruiserjunktion Cruiserjunktion@gmail.com Supporting Vendor GOLD Star

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    details

    Hello,

    The kit came with monte carlo calipers and new soft brake lines. I am reusing the oem rear drums. The instructions tell me to use a m/c from an 84 4wd p'up, and it has one resevior instead of two. The front brake line is on the top instead of the side like my oem piece. (see pic in link)

    I purchased 84 mc and installed it on the booster.

    It came with a pair of rubber tubes and plastic pieces that screw where the lines would mount for bleeding. The plastic pieces allow you to attach the rubber hoses for bleeding.

    I mounted the m/c on the booster and had some one else pump the pedal.
    I attached the rubber lines to the m/c where the hard lines would mount and submersed the hoses in a tub of fluid as buddy pumped brakes.

    As he pumped, bubbles emerged.

    When the bubbles stopped coming out the rubber tubes into the tub of brake fluid, I quikly re attached the hard lines to the m/c . I believed that this had filled the m/c and gotton out the air. I topped off the resevior and began the same process on the pass front caliper....... buddy pumping and me waiting for bubbles to stop.

    I then did the drivers side.

    I then did the passenger side.

    I then did the drivers side.

    etc....... the calipers don't move any. I do hear air hissing out of thecarb with each pump. Should't all pressure be going to the brake lines?

    My booster is a stock 71. I do not know "how to test" it....... so it hasn't been tested. I did replace the rubber seal that the vac tube attaches.
    I also have another booster from a 74. I am pretty sure it is working.

    thanks in advance

    mel
     
  7. cruiserjunktion

    cruiserjunktion Cruiserjunktion@gmail.com Supporting Vendor GOLD Star

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    Do I need to bleed the rears too?
     
  8. TonkaC

    TonkaC

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    If you have disconnected the lines to the rear, I assume you have since you are replacing the MC, you HAVE to bleed all 4 brakes. At the beginning you said you were going with all wheel disk brakes, and it looked like on the last post that you are reusing your drum brakes. The '74 I think has a 7/8" bore. I used the '95 TLC MC which has a 1" bore with the '79-'85 Booster. The '95 MC bolts right up to the booster. The '95 also has two brake line circuits that allow you to have brakes even if one end gets a leak, which I have had happen.

    If you are using the drums in the rear, I don't know for sure, but would think your setup should work once you bleed all four lines. Getting the air out should help it.

    If you are hearing air from the intake when the engine is off, that is ok. Your booster operates like a bellows pump if it doesn't have a vacuume. That should account for the air sound.
     
  9. too tall

    too tall

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    you won't notice the front working if you don't bleed the rears first.
     
  10. tornadoalleycruiser

    tornadoalleycruiser SILVER Star

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    On vehicle inspection:

    1 check air tightness
    - - start engine
    - - Stop engine after running for 1-2 minutes

    2 pump brake pedal several times.
    - -If pedal goes down deep the first time but gradually rises after the 2nd
    and 3rd times, it is in good condition.

    3 If there is no change in the pedal height when depressed the 2nd and
    succesive time it is defective.

    Check the operation:

    1 With the engine stopped, pump the brake pedal several times with the same
    pressure. Ensure that the pedal height does not change.

    2 Start the engine while the brake pedal is depressed, If the pedal goes down slightly at this time, it is in good condition. If there is no change in pedal height, it is defective.

    Check air tightness under load:

    1 With the engine running, depress the brake pedal.

    Then stop the engine while keeping the brake pedal depressed.

    2 Hold the pedal for 30 seconds. If the pedal height does not change, it is
    in good condition.

    If the pedal rises, it is defective.

    (I believe this is from the manual, haven't read one in a while tho)
     
  11. tornadoalleycruiser

    tornadoalleycruiser SILVER Star

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    Another thing, The drop hoses from the frame to the axle should be replaced as well sometime.. The kit probably came with the 2 knuckle flex hoses, good, they are new.. Now go look at your drop hoses, fold one over in your hand, look at all the cracks on the outside.. SCARY.. Now imagine how rotten it is inside? When they get old they will start to bulge when pressure is applied taking away valuable brake pressure as well..
     
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