MityVac issues

[planedick]

Once again

I posted this before, but I guess it went unnoticed. If you just take off the caliper and using large channel lock pliers, push the piston back as far as it will go while watching the resevoir fill up being carefull not to run it over, and all the bubbles that keep going up the line and refuse to come out the bottom will now go into the resevoir and your problems are over. Do both calipers this way and now all you have to do is pump the handle to push the caliper piston back to the point where the pads touch the disc, being careful not to run out of fluid in the resevoir. I did the vac thing first and had all the same problems you are having.

[Jarion]

That makes sense
same thing I do on the car when I put new pads on it.

[OregonRider]

The one disadvantage using a mity-vac is having air suck thru the bleeder threads. You don't have that issue when properly using the standard "old-fashioned" way, cause the pressure forces air and fluid out any leaky spot.
When using a Mity-Vac, I've always gooped Vaseline around the bleeder screw threads before cracking them open. The Vaseline is too thick to suck thru the threads and seals off air sneaking back in. When done it's easily wiped off and I've never had problems with Vaseline being sucked into the system.

[crazy steve]

I've always wrapped the bleeder threads with teflon tape; that cures the 'leakage' problem, and also prevents the bleeder from seizing...

[planedick]

Better yet

Air likes to rise up the hose in the liquid and pumping the liquid down the hose will not bleed it out because you can't pump it down the hose fast enough. Using a mity-vac is a little better, but you still have to move lots of liquid really fast to overcome the bubbles rising up the lines.

I have found that removing the brake cylinders from the mounts and using large channel lock pliers to push the caliper pistons in as far as they go will push all the air up to the master cylinder and out of the system. Lots easier and faster than all the pumping and sucking can, and no mess at all.

[fredintoon]

Adam, you could pull the front calipers off the forks.
Hang the calipers on something higher than the master cylinder reservoir on the handlebar and then try bleeding them again when most of the air bubbles are able to float up to the bleed screws at the calipers instead of being pulled down to them.

Hi Scott,
note that anyone doing this and not putting a suitable spacer, (5/16" plywood should work) between the brake pads will be one sorry bleeder.

[3Phase]

Hi Scott,
note that anyone doing this and not putting a suitable spacer, (5/16" plywood should work) between the brake pads will be one sorry bleeder.

Normally you'd be right, Fred -- belt, suspenders and everything! I used the Mity Vac trick when a front brake hose popped the night before I was leaving for a trip up to Canada and I didn't have time to mess around if I wanted to be on the road in the morning instead of playing silly buggers with the brakes.

I had one small bottle of brake fluid and the parts stores were all closed so I just pushed the brake pistons all the way into back the calipers and used the Mity Vac to slowly draw brake fluid up to the caliper bleeds from the front master cylinder without touching the brake lever, then closed the bleed screws and just let the calipers hang out for a while.

Every now and then I tapped on the calipers, hoses and fittings with a rawhide mallet to knock loose any trapped air bubbles while I finished packing and doing a bunch of other stuff I don't even remember. When I thought they were ready to go I gave them one more shot with the Mity Vac to get the last of the air out of the system before I put the calipers back on the front forks. I topped off the brake fluid reservior, then pumped the brakes until the pads seated against the brake disks and the lever was solid. There was no air in the system and I'd only used a little more than half a bottle of brake fluid.

Of course I didn't get more than a couple of hours or so into the trip the next morning before the stupid horn button fell off and the little metal remnant inside the switch housing kept vibrating and bouncing into the horn contact, honking the horn all by itself as I was riding down the road but that's another story!