Compressed air is (by far) easiest if it works, just use some rags to hold the juice and keep the piston from flying.
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Front disc brake question
- Thread starter Mikey
- Start date
If you use a grease gun, I found M10x1.25 nipples not easy to get hold of. Perhaps they'll be easier to come by where you are. In the end I had to buy a packet of 20!
Mikey
got muscles in his head that ain't never been used
There is a very good hardware store nearby that stocks a lot of metric bolts etc
You might be OK then. I found M10x1 and M10x1.5 nipples were everywhere. But M10x1.25 that I needed had to be hunted down! Good luck with it.
Mikey
got muscles in his head that ain't never been used
If I take the brake line off the MC and pull the lever and it squirts brake fluid it's ok ?
Depends if it works the same under pressure of applying the brakes hard. If you're overhauling the caliper, I would think about overhauling the master cylinder too. They are very easy to do.
Mikey when I use my HF bleeder I found that it leaked around the hose over the fitting. I wrap the bleed fitting with Teflon tape and it works much better. Sometimes it takes a few tries to get it to flow. Why do you think the caliper needs rebuilding? If it wasn’t holding pressure it I would think it would be leaking. If the problem is in the Master Cylinder I’ve also had good luck just cleaning them. I’ve used two of the kits that are sold and although they say compatible they have a shorter plunger and I have occasionally lost my lever pressure. A quick pump always corrected the issue but since then I just clean and reuse the stock parts and have had no issues.
I sometimes use a vacuum bleeder on the brakes too. When the bleeder to hose fit isn’t ideal, I usually adapt a proper fitting hose to the bleeder (use a stepped union between two hose sizes), then attach a small fuel line clamp. If you get leaking around the threads a wrap of Teflon tape on the threads usually seals it up enough to allow the vacuum to do its thing.
Mikey
got muscles in his head that ain't never been used
Using the HF bleeder it would keep negative pressure pretty good maybe 5-6 and it would hold it for awhile but just wouldn't draw fluid out of the system When I changed the handle bars out the line was tight until I took out the mounting clamp that held the middle of the hose to the bike
It just seems odd that with me just pulling on the line until I removed the holder that that would make the brake system go bad
It couldn't have happened because of my minor crash?
Time to take the caliper to the bench and rebuild that as I think I can do it without futzing any thing up
It will have to wait for a few weeks as it's time to doctor up
prostrate MRI and Khron's disease MRI and consult with the doctors (the Insurance. company's don't make money off me) then a weeks vacation
It just seems odd that with me just pulling on the line until I removed the holder that that would make the brake system go bad
It couldn't have happened because of my minor crash?
Time to take the caliper to the bench and rebuild that as I think I can do it without futzing any thing up
It will have to wait for a few weeks as it's time to doctor up
prostrate MRI and Khron's disease MRI and consult with the doctors (the Insurance. company's don't make money off me) then a weeks vacation
Like Wingedwheel, I have had to replace hardly any brake parts, just a good and thorough cleaning is all most needed. I've had a Mityvac vacuum pump tool for many years and think it works well, at least to refill an empty system. Yes, it sucks so hard that I get bubbles from air being pulled in around the loose bleed nipple, but it still pulls hard enough to get the fluid through. And since I get those air bubbles, I always finish the job the old fashioned way with a few hand pumps of the lever.
When changing the brake fluid, I first suck most of the old stuff out of the reservoir (using the Mityvac) and pour fresh stuff on top. No sense pumping all that old fluid through the system. I pull a couple reservoirs full through the system, finish with a couple hand pumps, and I'm good.
When I first installed an 11mm MC on my '78, I had issues with the lever pulling all the way back to the grip. Even though it wasn't leaking anywhere, I thought I might need to rebuild it because the seals might be worn and not generating and/or holding enough pressure. But then I discovered the hand lever was bent, not up and down but rather the normal outward curve it should have had wasn't there. It was bent straight, and that put it closer to the grip. So, I re-bent the proper curve into it and it's been good ever since, lol.
When changing the brake fluid, I first suck most of the old stuff out of the reservoir (using the Mityvac) and pour fresh stuff on top. No sense pumping all that old fluid through the system. I pull a couple reservoirs full through the system, finish with a couple hand pumps, and I'm good.
When I first installed an 11mm MC on my '78, I had issues with the lever pulling all the way back to the grip. Even though it wasn't leaking anywhere, I thought I might need to rebuild it because the seals might be worn and not generating and/or holding enough pressure. But then I discovered the hand lever was bent, not up and down but rather the normal outward curve it should have had wasn't there. It was bent straight, and that put it closer to the grip. So, I re-bent the proper curve into it and it's been good ever since, lol.
cough:
"The patented gggGary brake bleed technique; slave piston inserted just enough so the rubber seal is engaged. Fill slave cylinder with fluid through port, install line. NOW with port pointed up push in piston til fluid shows in master cylinder reservoir, top off reservoir, done. You can pump out piston, squeeze back in an extra time or two if needed. But usually once n done."
"The patented gggGary brake bleed technique; slave piston inserted just enough so the rubber seal is engaged. Fill slave cylinder with fluid through port, install line. NOW with port pointed up push in piston til fluid shows in master cylinder reservoir, top off reservoir, done. You can pump out piston, squeeze back in an extra time or two if needed. But usually once n done."
It's a good method. I did this a couple of weeks ago when I reassembled the front caliper and fitted new master cylinder and brake line. I had to draw some fluid from the bleed nipple but it was certainly a good way to fill a completely empty system for sure. I used a G clamp to slowly push the caliper piston inwards past a new square section seal.
Mikey
got muscles in his head that ain't never been used
I thought I had read your procedure before
Now it's bookmarked !
Mikey
got muscles in his head that ain't never been used
Now that's with a completely empty system ? as in line and master cylinder empty
sure but you are talking about rebuilding the caliper so those will be empty.
Mikey
got muscles in his head that ain't never been used
Yeah the calipers need to be rebuilt
I just didn't think that would be enough fluid to get all the way up to the MC
I guess the ID is that much smaller than the OD
I just didn't think that would be enough fluid to get all the way up to the MC
I guess the ID is that much smaller than the OD
You said your HF vacuum pump wasn't doing anything, but how were you using it? My Mityvac has a pressure gauge on it, and I think the HF one does too, so here's how I use it ..... first, loosen the bleed nipple then snug it back up. Attach the Mityvac hose and pump it up to like halfway up the scale then open the bleeder and let it drain down. Close the bleeder, pump it up again, open the bleeder, etc. After 3 or 4 bleed-downs, you should start getting some fluid out of the bleeder.
Mikey
got muscles in his head that ain't never been used
It's Harbor Freight so I could have a defective one as it will only go up to 5-6
Once I get the caliper rebuilt I'm to try Gary's technique first and have the bleeder as a backup
But I will return the defective one first
It's Harbor Freight you never know if the product is defective
My store is less than a mile from me so not a big problem
Once I get the caliper rebuilt I'm to try Gary's technique first and have the bleeder as a backup
But I will return the defective one first
It's Harbor Freight you never know if the product is defective
My store is less than a mile from me so not a big problem
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My HF vacuum pump has never given me a problem. Yours may only get to that negative pressure because at that point it’s drawing hard enough to pull air around the hose and fitting. Like 5t said, sometimes it takes a couple tries to get the fluid to come out. I also had to replace the oring around the waste reservoir because that was a source of leak down as well.
