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the mysterious brake situation

Discussion in '40- & 55-Series Tech' started by rusmannx, Aug 12, 2003.

  1. rusmannx

    rusmannx

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    some of you may have noticed that i've been struggling to get my brakes working.
    well, i tore my master cylinder apart to learn what i could, and i've decided that my problem doesn't lie within. since i was going to be draining my lines i thought it would be a good time to put on the extended braided lines, so i did, and they are very sexy.
    i fooled around with my booster, and have noted that it has good suction. when the master is off, with the engine running i can pull the push rod out and the vacume sucks it right back in with good force. i assume this is good, so i've decided the booster isn't the problem.

    my brakes seem to feel like they are always full of air, but have been bled 4 times from every concievable location, and i don't think that is the problem.

    here is what happens:
    the brake pedal goes to the floor. the resivours are full. i pump the brakes frantically and the resivour goes down 1/4 inch and the brakes get hard. i stop pumping and let the brakes sit for 10-20 seconds and the pressurized system depressurizes and the fluid that was pumped out of the res' flows back in.

    have any of you ever experience this?
    do any of you think it might actually be my booster or master?
    do any of you care?

    thanks again
     
  2. 73lndcrsr

    73lndcrsr SILVER Star

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    I wish I could say I have fixed this but,...

    I am experiencing the exact same issue on a '71 40. I have replaced the MC and wheel cylinders and bled them until I am sick of it.
     
  3. CruisinGA

    CruisinGA

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    Mine were like that when i bought the truck. 8 new slaves, one new master, one rebuilt booster later and they aren't really much better. There could be a few reasons other than bad M/C, Bad Booster:
    1-Bad wheel cylinder(s)
    2-Wheel cylinders aren't adjusted right, so you are having to pump the brakes to get enough fluid in the line to push them farther than they should have to be pushed. I can tell you the theory behind it and the physical steps, but apparently I do not have the genius required to adjust 8 wheel cylinders well. My mechanic does :D .
    If you have bad wheel cylinders I would just go discs. Might as well on all 4 corners. My buddy witha '78 with stock brakes stops on a dime, so much so that I nearly skid out every time I drive it cause his brakes are that much more responsive than mine. :mad:
    The booster is not related to the sinking pedal. Either M/C or S/C(s) are bad or out of adjustment.
    I've decided that the Toyota Engineers designed the 4 wheel drum brakes on a very sadistic whim :eek: ???
     
  4. rusmannx

    rusmannx

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    GA, you have matched my theory.
    i thought that i may have the brakes set to far apart so that i have to pump the wheel cylinders full. then, the springs are pulling them back (to far) and pushing all of the fluid back up to my master.

    tomorrow i am planning to take each wheel apart, expand the brakes until the drums will barely slide on. then hopefully things will be tighter.

    the reason i have the front ones seperated to the extent that they are is because after running for a while with them adjusted tight they would freeze up. i would then have to crack the bleeder valve to release the pressure. i guess i'll just have to tighten them up and see if the problem still exists.

    any other takers?
     
  5. JohnL

    JohnL

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    I didn't see if you have already adjusted the cylinders at each wheel?

    I did what you did on my 74, had the drums turned, kept OEM pads (good condition), added ss brake lines, and it stops on a dime, straight and fast.

    Expand each cylinger one-by-one until the one you are working on is rubbing, then back it off 1 click. Repeat on each cylinder. Drive it around for a while, go back and do it again. You should be good then.

    John
     
  6. JohnL

    JohnL

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    PS. You don't have

    to take your wheels apart to do this. Just jack up one wheel at a time and adjust the "clickers"

    HTH
     
  7. CruisinGA

    CruisinGA

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    [quote author=rusmannx link=board=1;threadid=4288;start=0#msg31791 date=1060724006]
    tomorrow i am planning to take each wheel apart, expand the brakes until the drums will barely slide on. then hopefully things will be tighter.
    [/quote]
    Unless you want to for other reasons, I wouldn't take the drums off, just do what JohnL described, jack up a wheel, adjust the clicker till you hear a scraping sound when you move the wheel, and then back off one click, then repeat for the other 7 cylinders.
    JohnL -I haven't had my drums turned yet, I might try that before I trade in for disks, how much did it run you, and do you think a Napa with machine shop service could do it?
     
  8. dd113

    dd113

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    I have drums on my 73 and it will stop on a dime. Much better than my 62 with all new brakes. My other 73, with all new brakes, all parts new, stops OK but not perfect. Who knows why as they are exactly the same. A few ideas: make sure the pedal ht is correct. Make sure your booster pushrod is adj correctly, check pedal freeplay, make sure the shoes are on in the correct direction, when adjusting the brakes I cannot see how you can be accurate with the wheels on, I put the whold thing on stands. You must hold the drums to the studs with lug nuts to get an accurate adjustment. Start it up in 4wd and apply the brakes a few times, this will set the shoes.Adj each cyl until it will not allow the wheel to turn, back it off until you hear a solid scraping, repeat. If you think you have it a bit tight you are there. Start it up again and apply the brakes in 4WD. check the adj. You may need to do this more than once. Once it is all adjusted bleed them again.
     
  9. JohnL

    JohnL

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    CruisinGA & David...

    Cruisin: you should get them done for about 10 each at Napa. Unskilled labor, NAPA is OK. Important to have round drums to get good stopping. You can tell upi are out of round if as you are adjusting your wheel cylinders you get rubbing in some spots on the wheel as it rotates, but no rubbing elsewhere.

    David...wanna help with my elec ?...here or CCOT...please?
     
  10. CruisinGA

    CruisinGA

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    [quote author=dd113 link=board=1;threadid=4288;start=0#msg31836 date=1060737385]
    make sure the pedal ht is correct. Make sure your booster pushrod is adj correctly, [/quote]
    How do you do this? I have a new booster and it may not be adjusted correctly. Also, now sometimes after I pump my brakes once, I will push and they will start to stop, but then it feels like the pedal is letting off a ledge and then it sinks in about 1/2 the way in and gets very hard, like manual brakes. Tomorrow I'll try the adjusting method you describe. Also, I've been using a standard open end wrench for the bleeders, I heard there is some wrench made specially for this?
    Rusman-Sorry to partially hyjack your thread, but I think these are fairly relevant questions.
     
  11. JohnL

    JohnL

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    I never rebuilt the master, so I don't know

    if your problem is there. Any wrench is OK for the bleeders, but a closed end will diminish your chances for rounding it off. I actually thread the bleeder hose through the closed end of the wrench, fit the hose over the bleeder nipple, then slip the wrench down over the plug.

    Haynes is very clear and has pictures on this. THat will help you more than my dialog here....
     
  12. dd113

    dd113

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    pedal ht is adjusted by the pushrod. Remove the spring and measure as per haynes or Toy book. About 9.5" is correct off floor. You might need to loosen the stop light switch. This requires SST: 3 handed midget. For the pushrod there is a cool SST that sets it for you. If you are installing a new MC or booster you need to set it. It really cant move much on its own so dont worry about it if nothing has been changed. Easy way to adj is to put MC in place and feel if you get any resistance when it goes flush against the booster. If is pushes back at you shorten it. Keep making it longer until it pushes back then back it off 1/2 turn. You can tell if it is too far out is the brakes get progressivley harder as you drive, eventually they will lock up. No need to remove the hard lines to adj. Just do the old trial and error. Too far out and your booster will not be able to give full boost and your pedal travel will increase. Free play is just how much slop you have in the pedal before it hits the booster piston. With the MC pushed to the side push the pedal and see when the booster pushrod moves. pedal should move around a 1/2" or so. The spring keeps the pedal/pushrod from hitting the booster piston.

    Hard to say exactly what causes your problem. I bet it is rod adjustment.

    You are talking about a line wrench. Essential for most all brake work except bleeder screws. Just do as John L describes.
     
  13. CruisinGA

    CruisinGA

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    I bet that it is pushrod adjustment, and my brake light switch needs adjusting anyway, I remember that when I installed the booster, I didn't feel anything at all when I bolted up the MC. I'll check all that out tomorrow. Thanks a ton David.
    I guess I should have used a line wrench when I replaced the rear brake line? :eek: :-[ .
     
  14. dd113

    dd113

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    You should not feel any resistance. That means it is correct or too short. There should be around a 1/16" gap between the booster pushrod and the MC piston. I have tried measuring the depth of the hole and the length of the pushrod and subtracting the 16th but I still end up going trial and error. BTW: New booster, did you install the GM line filter. I think the number is on here
     
  15. CruisinGA

    CruisinGA

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    [quote author=dd113 link=board=1;threadid=4288;start=0#msg31878 date=1060743574]BTW: New booster, did you install the GM line filter. I think the number is on here
    [/quote]
    GM line filter? Come again?
     
  16. thorvald

    thorvald .......

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    rusmann, you didnt mention if you bench bled the master cylinder, if not, from what ive heard, youll never get all the air out, just a thought
     
  17. megolfer

    megolfer

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    I had a similar problem and finally got it fixed after many hours of frustration. It took 3 new MC to get it fixed. I got 2 MC's from CCOT and they were both bad. I finally got a rebuilt master from a local parts store and it fixed the problem. It seems to me that these aftermarket MC are low quality and not worth a crap. 3 weeks to get a good mc.
     
  18. hammerhead

    hammerhead

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    I fought with TLC brakes so many times I was convinced that disc was the only way to go. Then I got a factory Toyota Land Cruiser chassis & body manual. I went through the brake system performing only adjustments, but doing everything to the letter, by the book. I wanted to prove that these were the worst brakes in the world and that I needed to install disc brakes before any other mods. This book proved me wrong. My drums work so well I have pushed discs way down my priority list. My vacuum booster recently started failing and they still work so well I haven't worried much about it. Don't take me wrong. I still want disc but it isn't near as important when your drum system works so well.
    BUY THE GENUINE TOYOTA MANUAL. The rest pale in comparison and its a lot cheaper than replacing unnecassary parts. Besides, it covers the whole rig from top to bottom, from front to back, and things in between that you didn't even know were there.
     
  19. rusmannx

    rusmannx

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    thorvald;
    i don't know what this bench bleeding of the master is you speak of.

    hammerhead;
    is this the green manual you speak of?
     
  20. rgentry

    rgentry

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    My '68 has 4 wheel drums and the single master
    cylinder. I had the drums turned (even if they
    are new, have them turned!), new shoes, and
    adjusted them according to Jeff Zepp's instructions.
    These are available here on this site under
    "Technical Links". Once the shoes set in, after
    say 1000 miles, I tightened them a tad more.
    No brake problems at all. I can lock all 4 -- what
    more do I need?