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Discussion Starter · #1 ·
On the way home from work the other day my rear brake started grabbing which I noticed in between gears while shifting. Checked brake fluid and it was topped off. The next morning I had no rear brake until it was almost floored. I tried bleeding it with a miti-vac and can't even get fluid out. The pedal had no resistance. Could it be a master cylinder bypass issue? There is no leak. Bike is a 1996 Ultra Classic. Dead in the water. Anyone have a clue?
 

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Do you know when the last time the brake system was flushed and new fluid put in? I think '96's used DOT5 which can get pretty nasty when old. Rear master cylinder rebuild kits are inexpensive and fairly easy to install.
 

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Discussion Starter · #3 ·
It was flushed just last year when I bought it. Harley replaced the master cylinder since the one on it was faulty. Can you rebuild a master cylinder on a 96 fl model?
 

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On the way home from work the other day my rear brake started grabbing which I noticed in between gears while shifting. Checked brake fluid and it was topped off. The next morning I had no rear brake until it was almost floored. I tried bleeding it with a miti-vac and can't even get fluid out. The pedal had no resistance. Could it be a master cylinder bypass issue? There is no leak. Bike is a 1996 Ultra Classic. Dead in the water. Anyone have a clue?
Your brake caliper piston is sticking.. new ones are cheap,,, but the 2 seals are the tricky part
 

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I had to purchase a vacuum bleeder from cycle shack to pull fluid thru to fix my bike.
But my pedal was going all they way down, I didn't have any sticking. I had a friend go down when his rear tire locked up on the freeway.
 

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Discussion Starter · #6 ·
I used the vac pump on the rear caliper but I couldn't get any fluid out. I pumped it up to around 20 and it would drop like it was pulling but no fluid in the hose and the reservoir stayed at the same level. The seal was good because it didn't drop until I opened the breeder screw. I'm thinking maybe the plunger in the master cylinder may be stuck not allowing fluid through. The rear wheel will spin freely so the piston is not stuck but might not hurt to rebuild it anyway seeing as the bike is nearly 20 years old.
 

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Try pedal bleeding. Pump, pump, pump and hold, crack bleeder and close. Repeat until fluid squirts from the bleeder. Do this procedure with the lid off the master cylinder and topping off the fluid as it goes down. If it goes dry air will get into the line.
 

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CVFFCV
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Try pedal bleeding. Pump, pump, pump and hold, crack bleeder and close. Repeat until fluid squirts from the bleeder. Do this procedure with the lid off the master cylinder and topping off the fluid as it goes down. If it goes dry air will get into the line.

Sometimes this is the only way to do it. I bought an older Toyota Supra once that had horrible brakes. I sat at each wheel with a vacuum pump for a good 20 minutes per and didn't get anything out of it. A buddy of mine (old school mechanic - does timing by ear type of guy) told me to pump the brakes while he does the valves and tops off the fluid. Lo and behold, after a few rounds of pumping brakes, it blew chunks out of the valve and I had pressure on the brake pedal, finished off the other 3 wheels, and brakes were perfect. Air and chunky old fluid were the culprit, the vacuum pump just didn't have what it needed to get it out so the clean fluid could do its job.
 

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Do not use DOT 5 !
It will always give you a Cadillac soft peddle and is very very hard to bleed.
 

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Do not use DOT 5 !
It will always give you a Cadillac soft peddle and is very very hard to bleed.
:what? :think
I always use DOT 5 and only DOT 5.
Much more moisture resistant and anti-corrosive.

Even went to DOT 5 years ago on a few cars I liked a lot and planned on keeping for a very long time.
Was a PITA making sure I had a complete flush. But worth it in the end. IMO
 

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You will find DOT 5 is not much pleasure in a canyon run or spirited driving..
 

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I guess if the riding harder, longer further is the trump card, I have been on a bike since 1964.
Back to seriousness
We tried dot 5 in our race cars and learned the hard way.
Do as you all wish.
 

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Wayward Son
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I guess if the riding harder, longer further is the trump card, I have been on a bike since 1964.
Back to seriousness
We tried dot 5 in our race cars and learned the hard way.
Do as you all wish.
Not trying to compare time in the saddle. Just saying I`m not a johnny come lately.

Race cars on a closed course, under the constant extreme conditions they face are a bit of a different beast then open road in a car or on a bike.

Agree to disagree and carry on. :)
 

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Discussion Starter · #16 ·
I pulled the master cylinder and pulled it apart to find what looked like grease in there. I cleaned it all off and re assembled. Did the pump the pedal while vacum bleeding. Went well. Today I rode all day just to have the same thing happen again. Do I need to replace everything and rebuild the caliper? Would the caliper sticking cause the plunger to stick in the master cylinder? I'm assuming replacing the hose is not out of the question also.
 

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Rubber hoses will typically collapse in the inside causing brakes to drag.
Seems to me throw it all on the bench and do what has to be done .
 

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Discussion Starter · #18 ·
Pulled the caliper and there is no signs of leakage and the piston moves freely with a small amount of air introduced. Ordering a decent Russell or Goodridge stainless rear line. It's the only component left. Thanks guys for letting me talk this out without ribbing me. Appreciate the helpful advise.
 

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The grease in the master cylinder is assembly grease, should also have been in the caliper. A grease packet is usually always included in the rebuild kits as well.
 

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Having the brakes heat up while riding and then having more and more drag as they heat further almost always indicates a plugged compensation port in the master cylinder. Does the pedal come fully back up when released? If not the plunger in the master is not coming fully out and exposing the compensation port thus trapping the fluid. If the pedal is coming fully up the port is plugged with foreign matter. It is very small, the hole in the bottom of the reservoir where the fluid enters the cylinder containing the plunger. Something very tiny can block it.
 
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