MityVac issues

[xs1100newb]

Ok,
i have spent countless hours trying to bleed the front brakes on my 1100F. I went out and bought a mityvac today from the local autoparts store and I spent 40 dollars on it. It hasn't helped at all.

Here is what I am doing.

First I bled the MC according to the instructions in the manual. (This was done because I am starting with an empty reservoir.)

I put a plug with a hose adaptor onto the outlet port, filled the reservoir, then kept pumping the might vac until I did not see any bubbles coming up from the reservoir.

I then connected the brake line to the MC outlet and proceeded to bleed the left caliper.

I connected a 3/16" hose to the bleeding screw, then connected it through an adapter to a larger house which fits the mityvac products. I pumped the mityvac until I got a good vacuum, then loosened the bleeding screw. I get a frothy mix of brake fluid. I then closed the bleeder screw and repeated the process.

I kept doing this and I could never get rid of the frothy mix. I am pretty sure it is because my connection at the bleeding screw is sucking in air when I create a vacuum. What can I do to seal this? I tried teflon tape, but it appears to dissolve in brake fluid.

I am really at my wits end.


Adam

[crazy steve]

Adam, pull the bleed screws out and wrap those threads with teflon tape. That's where you're sucking air, and once you do that it'll go much better. Been there on this one...

[benxs1100]

I'll second crazy steve on that one.

[xs1100newb]

I put teflon on the screws and it helped a ton. I am no only pulling liquid. I pulled an entire mityvac cup of liquid through each caliper, however, the brakes are still weak. I also took a rubber mallet and tapped all the connections to jar any bubbles loose. Any other ideas?

Should I be working the lever at all when operating the mityvac?


Adam

[Ken Talbot]

I use a mighty-vac too, and it is a great tool for flushing fresh fluid through the system.

I have also run into the same problem as you when trying to bleed the system, and IMHO, here's why:

You charge up the might-vac, crack the bleed screw, and watch carefully as the fluid level drops in the master cylinder. When the fluid level gets almost empty, you shut the bleed screw, refill the reservoir, and rechgaege the mighty-vac. In the time it takes between shutting and opening the bleed screw, the air bubble that you have been sucking downstream in the lines, floats naturally upstream. Depending how long between cycles, the bubble(s) float back up as high as it(they) was(were) when you started. All you're doing is pulling nice fresh past the sir bubble, out the bleed screw, and throwing it away. If you bleed too slow, there is not enough flow past the bubbles to dislodge them and pull them through the system.

So, you gotta be quick, and a bit bold to do this successfully. Have your fresh fluid handy, have lots of rags under the reservoir just in case, start with an empty reservoir on the mighty-vac, and use a box-end wrench on the bleeder screw so you can leave it in place jammed on under the vac hose. Pump up the mighty-vac, crack the bleeder well open, and start adding fluid to the draining reservoir. As soon as the vacuum decreases, crank it up quickly, and get back to topping up the reservoir, all the while keep an eye out for the offending bubbles. Keep at this for a bit then close the bleeder screw and check your progress.

An extra set of hands, i.e. a friend, can help by running the fluid top-up while you worry about the vacuum end. Bottom line - get and maintain a good flow in the lines to dislodge the bubbles, while keeping the reservoir from running dry. Simple, really, eh?

[3Phase]

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.

[petejw]

hi adam,
u shouldnt need the mity vac to bleed the brakes,
i posted on your other thread regarding bleeding,
have you tried that method?

also if u let the m/c accidently run dry then ull have
to rebleed the m/c again,

something else comes to mind , when u crack the bleeder u only need to turn
it a quarter of a turn if that.

you should be able
to bleed the whole system within minutes.

[DGXSER]

Yes, the Mity vac works great for establishing fluid to all the areas. Once you can pump the brake lever/pedal and get pressure to develop, put the mity-vac away. From her eon in you just need to do the bleeding techniques mentioned.

For the air in the lines that is trying to float back to the MC, that is the reason for the method of strapping the brake lever pulled on and leaving it there. With the plunger depressed it opens the path to let the air get up into the reservior.

[DAVINCI]

For the air in the lines that is trying to float back to the MC, that is the reason for the method of strapping the brake lever pulled on and leaving it there. With the plunger depressed it opens the path to let the air get up into the reservior.

I've read this a few times here and I still don't understand how that works. If this is true, wouldn't it then be true that fluid is getting back to the MC while the lever is pressed? If so, then how could the brake work at all???

[Eveready1100]

I haven't had to do this on my 11, but I've run the bleed lines back up to the M/c, then cracked the bleeders as per Pete's post so as to let fluid through, but with a little resistance, then just slowly pumped the brake lever, cycling the fluid around and around the system till no bubbles are left in the lines. Then with the lever squeezed back to the bars, close off the bleeders. You should now have a firm lever.
Be careful of fluid squirting up out of the spooge hole. Take your time and all should be well.

[cywelchjr]

I've read this a few times here and I still don't understand how that works. If this is true, wouldn't it then be true that fluid is getting back to the MC while the lever is pressed? If so, then how could the brake work at all???

I've never understood that one either. It seems to me that just getting things into the right position so that the air could work up into the MC might work, but I have my doubts about that too, otherwise you wouldn't need to do a bench bleed after a rebuild.

I'm thinking the first full rebuild on mine (will coincide with braided SS lines) the bleed will be done off the bike, then everything installed with it all connected, so the calipers will be higher than the MC while the bleeding is being done so that the air will naturally want to go to the bleeder. I don't intend to fight with the air in the least.

[DGXSER]

to be honest I had to rethink my theory there as well, I believe the pressure is the key to holding the lever, so your "squeezing" the air and encouraging it to move, Gravity will make it move up then. So I agree, the movement of the plunger does not open a passage, just adds pressure in the system.

[MaximPhil]

to be honest I had to rethink my theory there as well, I believe the pressure is the key to holding the lever, so your "squeezing" the air and encouraging it to move, Gravity will make it move up then. So I agree, the movement of the plunger does not open a passage, just adds pressure in the system.

Hi DGXSER,
"Gravity will make it move up" First I think Newton just lost his apple Reminds me of my late brothers photograph caption: "Looking EAST as the sun sets" Which turned out to be a picture of Sunrise after a night of drinking Cider. His sense of direction was still good though his time of day was off.
Phil

[DGXSER]

Phil, you got me, I really have to rethink posting here after 20 hour days with six hours of driving. At least until I have had a nap. How about substituting bouancy for gravity there.

[Incubus]

I use a power bleeder like a mityvac when I bleed the brakes on my bikes, Newb, but I do a kind of hybrid operation. I put vacuum on the lines, but then I bleed the brakes just like normal, pumping the lever and cracking the bleed screw with pressure on the lever. Go back and forth between the two calipers several times. I can bleed the front system on my XSes from an empty system to a firm handle within 10 minutes.

Patrick