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HELP Brake issues with the 86 Brat


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Half way through a drive I noticed that I had to depress the brake pedal much farther before braking began (they worked fine when I pulled of of my driveway). The brakes acted as if they needed to be bled. I didnt get around to it and a few days later the left rear wheel cylinder broke and by the time I made it home all of the fluid had leaked out of it. I replaced both rear wheel cylinders and brake shoes and bled the brakes at the master cylinder and all wheels in the correct order. Yet in order to get any braking power, i still have to pump the pedal 6-8 times and even then it sucks. Sometimes it pulls hard to the left, sometimes it doesn't. Needless to say, I won't be driving like this. Could this be a problem with the master cylinder? There are no fluid leaks. ANY advice would be appreciated!! Thanks!

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Brakes can be funny painful sometimes. I like to clean out my bleed screws holes to ensure they will bleed nicely, then have had to use good thread tape like gas or plumbing tape on the threads just to ensure no air sneaks back. My one man bleeder is soft rubber hose for the nipple, coupled to a clear PVC hose that must loop up first before it comes down to drain into an old plastic poison bottle, through the lid with an air breather hole next to it.

 

This way you can watch the crud and the bubbles. This method is gravity feed bleed with occasional one man foot press while bottle does the job of collecting air and fluid. A tip is always allow pedal to return slowly or airmanages to get in at the master !

 

Wonder if a near thirty year old hose has collapsed internally  ?

 

84 Brumby with Portland Disc Rear

Edited by jono
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I didn't have much daylight yesterday so it was admittedly a "that should probably do" bleeding job with a state inspector friend of mine who has done this more than I have. He just let me know that a book at his shop has a different bleeding sequence than the one my repair manual specified yesterday, even though they are for the same vehicle... Today I will bleed it again more carefully after I figure out the correct bleeding sequence... Thanks for the suggestions

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If the MC ran dry you maynneed to bench bleed it, which you can accomplish by removing a line form te MC itself and plugging it with your finger, letting fluid pass thru, but your finger stops it from sucking in air.

 

Bleed from the LR, RF, RR, LF

 

IT will help to depress the clutch cable (hill holder) when bleeding out the rear wheels

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You also need to adjust the rear shoes.

 

They are manual adjusting.

 

ON the back side of the backing plate, near the bottom there is a rubber cap.  Pull it off and it reveals the adjuster screw.

 

Now it's not a simple screw, it has 2 beveled sides, and those faces interact with the adjuster pins.  Each 1/2 turn aligns the faces.

 

Jack up a rear wheel.  Spin the wheel and turn the adjuster screw gradually one step at a time until the shoes begin to drag and hte wheel slows spinning.  Back off one turn after that.

 

After you've done that....then bleed as per above.

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Well I found out the bleeding sequence in the repair manual was wrong, thanks MilesFox.  I just used a clear siphon hose to the brakes in that order since I didn't have a partner and the brakes are working perfectly again. There was still a ton of air in the primary lines.  Didn't even need to mess with the master cylinder, I'm pretty relieved.  Thanks guys

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Sorry, i must correct myself, start with the RR, LF, LR, RF. The idea is bleed the wheel farthest from the MC. This is a dual diagonal braking system, where the LF and RR are ganged together and vice versa. This is sort of arbitrary, as long as you start with the rear, i suppose. Sometimes oyu can do it FF, RR, but keep the dual diagonal in mind. I guess it all depends on which one has air in it. And depressing the clutch for the hill holder is the magic trick that is not described in any procedure.

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I used the clutch trick, but how does this help? I haven't read up much on this hill holder thing, but sometimes when I back down my driveway (which is at a slight slope), if I push the clutch in while slightly braking the hill holder will kick in and jerk me to a stop. Any info on this?

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When clutch is depressed hill holder acts as a one way valve(ball valve, active only at upward angle), holding any pressure that is applied to the brake circuit.

 

When clutch is released, a pin protrudes into the chamber and keeps the ball from blocking seat/holding presure.........press clutch, pin is pulled back, and if the nose is up, the ball rolls into the seat, locks pressure.

 

Simple mechanism, only thing that can really fail is the seal on the pin shaft.

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