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Help with stopping power

Discussion in 'General Truck Info' started by Smf834, Oct 15, 2020.

  1. Smf834

    Smf834 Member

    So i am new to this website, learning a ton as i read, and few members here have been very gracious in sharing their knowledge.

    With that said, i have a brake problem. My 91 sambar that i just got, the brake is completely gone, as is, when i depress it, spring pressure only when key is in “on” position. Reservoir is clean, i took the steering center pad off, but unable to go further in removing the steering wheel, and so forth. I have sprayed some penetrant on the bleed valve, because they are all stuck pretty good. I experienced stuck brake prior to this, do you think is related?

    So what should be my plan of attack? Remove the master cylinder? Start bleeding the brake?

    any advice is much appreciated!
     
    Last edited: Oct 16, 2020
  2. SAITCHO

    SAITCHO Active Member

    Start from the easiest and less costly first. I would flush the brake fluid first and continue from there.
     
    Limestone likes this.
  3. Limestone

    Limestone Well-Known Member

    I agree with SAITCHO, BLEED THE BRAKES! Least evasive!!! Penetrating oil is good,(PB Blaster,Kroil), on the bleeders, take your time with them, and let the fluid do it's job! If you clean the rust and gunk off the bleeders, with a wire brush, it helps, a lot to remove them!
    Limestone
     
  4. Smf834

    Smf834 Member

    Is there a way to bleed the brake without any brake pressure? Probably need a pressure/venturi setup?
     
  5. Jim Nelson

    Jim Nelson Active Member

    Get a Mighty Vac or the cheaper knockoff from harbor freight. I used one to replace the fluid in my mini., just start at the wheel closest to the master cylinder and then go to the other front and do it. Keep an eye on the fluid level and don't let it get down or you will suck more air in. On some of these trucks there is only one bleeder in the rear so it will take a little longer to do.
     
    Limestone likes this.
  6. Smf834

    Smf834 Member

    Got the brake bled first time, lots of old fluid out, got rid of lots of air bubbles. Still no brake pressure. Will try to bleed the system again.
     
  7. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    It is probably a bad master cylinder.

    How thick are your front pads? The most common cause of bad master cylinders is someone forcing the campers to compress so they can slip in new brake pads, without opening the bleeder to let the fluid escape. This forces things back into the master cylinder. Which then causes the seals in the master cylinder to fail.
     
  8. Smf834

    Smf834 Member

    the front pad looks ok, albeit very stuck to the wheel it seems. The rear wheel has more free motion. I suspect the front brake is stuck.

    so take the front calipers off or try to get the master cylinder off first? I still couldnt get the steering wheel off, even though the nut is off
     
  9. Limestone

    Limestone Well-Known Member

    Get the proper steering wheel puller! Maybe you can rent one for free, from Auto zone, or the other cut rate auto parts, Sheisters out there!
    Limestone
     
  10. Smf834

    Smf834 Member

    I finally managed to pull the master cylinder out. It didnt seem to be in bad shape. Oring still intact. I do question the part of the cylinder where the booster inserts into, it seems to be solid, conical shape, seems stuck, and i assume that caused my stuck brake?
     

    Attached Files:

  11. Limestone

    Limestone Well-Known Member

    Hmmmmm!
     
  12. Koffer

    Koffer Active Member

    Yeah , that sure can be your problem
     
  13. Smf834

    Smf834 Member

    So is that grey conical shaped inlet supposed to move freely? How can i untangle it?
     
  14. Koffer

    Koffer Active Member

    91FB953E-0ABC-433A-B54E-9903BD4EEE18.png
     
    Limestone likes this.
  15. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    If by gray conical thing you mean the piston: No it doesn’t move freely, because the seals will be against the cylinder causing friction. But it should move with a bit of friction.

    You may be able to impact it out by slamming the cylinder against a block of wood. I’ve been able to get some of them out with a set of snap ring pliers, by reaching in and catching the tips on the inside where the actuator rod goes in.

    Last case scenario is to push it out with compressed air. If you try that method, you need to screw a piece of plywood to it using the flanges where it normally bolts on, and leaving just a 1/4-inch gap. And, you will need to block all but what would most ally be the front outlet, so the air doesn’t just whistle out the other holes.
     
    Limestone likes this.
  16. Smf834

    Smf834 Member

    So i have another master cylinder ready to be put back. Should i do fill the inside with brake fluid, and what is next step?

    Also, i am trying to diagnose why the front brake seems to be dragging. I couldnt remove the caliper bolt, it seems to be in between 18-19mm. I even located a 18.5mm, and it is still a tiny bit loose. The front wheel takes a lot of effort to spin right now with no brake pressure
     
  17. Jim Nelson

    Jim Nelson Active Member

    In the old days we would fill and bleed the master cylinder before installation. As far as the caliper I can't help but pretty sure you need to get it loosened up.
     
  18. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    Can you drive a 6-pt, 18-mm socket onto the bolt head with a hammer?

    I had to drive a 19/32 socket onto a 5/8-inch bolt head back in my youth to get the stuck caliper mounting bolts loose on a Sunbeam Alpine.
     
  19. Smf834

    Smf834 Member

    Its pretty tight but i may give that a try. I tried hitting the caliper metal frame with a hammer, hoping it may unstick things a bit. The truck starts and drive ok, at least front brake doesnt seem to be dragging significantly (previously car would lurch to a stop as soon as i let go the gas pedal).

    So i install a new master cylinder, it seems to function properly when i move in the piston, fluid squirts out from the 2 outlet. And then i pressure bled the brakes again, the pedal now doesnt go all the way with no resistance, but still no real brake pressure...?
     
  20. Limestone

    Limestone Well-Known Member

    Smf,
    You need to address these issues with your brakes! No ! Seriously All of your brake mechanism's need to move freely! not close, or maybe! C'mon these are your brakes!!! Don't be afraid to get your hands dirty, and let's go! Every contact point needs some kind of lube! Different lube's for different applications! Remember, use common sense, because brake dust, and dirt will stick to everything! That's why in many cases a dry lube is better! Like a spray graphite! It goes on wet, and dries to a nice uniform graphite film! You should be getting fluid from all your, ports, bleeders when bleeding it properly! If your lurching to a stop when you de accelerate your shoes are hanging up, re...pressure from caliper, shoe, cylinder not working smoothly! Smooth like a baby's bottom!!!
    Limestone
     

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