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Brake bleed problem

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Pulled calipers apart. Pulled pistons from bored, pulled pins, pads, etc. Put brake fluid on caliper bore seals, put it on pistons, slid them in by hand, no problem.

Go to bleed lines since they're empty, and I've tried everything. Pistons refuse to move and tighten to disc. 

I used mityvac, tried manual, nothing. Kept pulling fluid out. Must have refilled master 8 times. Still no pressure. Air should be out. What's the deal?

Brake lever: pump, pump, pump, hold to handlebar, crack open bleeder, close before fluid stops. Repeat 100 times, nothing.

 

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4 hours ago, Kwest364 said:

Pulled calipers apart. Pulled pistons from bored, pulled pins, pads, etc. Put brake fluid on caliper bore seals, put it on pistons, slid them in by hand, no problem.

Go to bleed lines since they're empty, and I've tried everything. Pistons refuse to move and tighten to disc. 

I used mityvac, tried manual, nothing. Kept pulling fluid out. Must have refilled master 8 times. Still no pressure. Air should be out. What's the deal?

Brake lever: pump, pump, pump, hold to handlebar, crack open bleeder, close before fluid stops. Repeat 100 times, nothing.

 

I use a large syringe and pump the fluid from the bleeder at the caliper, up to the master cylinder; messy, but effective.  One thing of note, make sure your piston in you master cylinder is returning all the way to the rest position.  If it doesn't, it won't uncover the fill hole in the master cylinder bore.  Dirt/crust build up can prevent the piston from completely returning.  Nissin master cylinders are slow fill, meaning when you pump the brakes to bleed them, as the master cylinder piston returns to the rest position, if you pump too fast, there may not be enough time for the fluid from the reservoir to fill up the piston bore.  Make sure there is no black mush (deteriorated rubber seals mixed with brake fluid) in the bottom of the master cylinder covering the fill hole that goes into the master cylinder bore.  Also, the piston in the master cylinder is small, so when you release the bleeder, there isn't much in the way of velocity and volume to carry a lines worth of fluid and air out of the bleeder.  Air can set in the line a gurgle around and not move on out.  The syringe method works well for me.

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Lots of tapping on the line and the caliper, whether I reverse fill or not. A clean caliper filled up with the Pistons at Max safe extension works good as a back bleeder. Hanging the caliper above the master cylinder can work. Again, tap to free up the bubbles.

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I'm gonna try reverse bleeding. Seems the most sure fire way. A little bit more prep, but I'd rather use a method that is easy, effective, and smooth sailing. Less that can go wrong the better. I've seen people put zip ties on caliper bleeder to hold tube on. I'm gonna try a hose clamp. Should work really well and get it nice and tight. 

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43 minutes ago, ossagp1 said:

Lots of tapping on the line and the caliper, whether I reverse fill or not. A clean caliper filled up with the Pistons at Max safe extension works good as a back bleeder. Hanging the caliper above the master cylinder can work. Again, tap to free up the bubbles.

What do you mean by clean caliper filled up with the pistons at max safe extension? Normal rule of thumb is to insert pistons all the way into boxes, then after fluid in line, pump lever to create pressure and push pistons out of bores until pad moves over enough to make contact with caliper. Are you suggesting starting with pistons already extended out? Why? Couldn't that lead to potential pockets for air to go?

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You fill the caliper with the Pistons extended to get maximum volume. Then t you collapse them slowly. It fills the line and the master cylinder. Not my favorite way. 

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When doing "back bleeding," use a clear vinyl tubing to the bleeder nipple. This way, you can see if you are pushing air back into the system. Go to a horse feed store and get a couple huge horse syringes for brake fluid. They work great for this. 

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17 hours ago, Kwest364 said:

I'm gonna try reverse bleeding. Seems the most sure fire way. A little bit more prep, but I'd rather use a method that is easy, effective, and smooth sailing. Less that can go wrong the better. I've seen people put zip ties on caliper bleeder to hold tube on. I'm gonna try a hose clamp. Should work really well and get it nice and tight. 

If you're using a ring spanner. Don't forget to put the spanner on the nipple before the hose and clamp/zip-tie :D

Edited by Drop-Bear
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