Brake bleeding with Mityvac

[Reid]

After much swearing and wasted DOT 4, I gave in and bought a Mityvac system to bleed my brakes. Half a roll of PTFE tape later and I've finally got the Mityvac to create a proper vacuum along it's length, only issue now is getting it to seal properly over the bleed nipples. When trying to bleed the system it draws through as much air as it does fluid and I'm presuming it's allowing air back into the calipers at the same time. PTFE tape around the bleed nipples isn't working so has anyone got any ideas on how to create a seal without permanently damaging the bleed nipple or the Mityvac's adaptor?

Cheers,
Jon

[Bezzer]

Tube on the nipple?? cheapo one way tubes sometimes have a piece of plastic with them with a hole in it that fits over the pipe and you can push it down over the nipple to clamp/seal the tube to the pipe if that's what you mean, you could find something with the right size hole to do the same job or just use a small cable tie to clamp it on.
As you've found the mityvac principle is fine but such a bitch to make everything airtight so it actually works and not worth the trouble a lot of the time.
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[Kickstart]

Hi

I have a MitiVac as well. While very useful for initial bleeding of an empty system (where a bit of air drawn around the bleed nipple threads doesn't matter) I tend to finish off with conventional bleeding. Pull lever hard, crack off bleed nipple and retighten then release lever.

All the best

Keith
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[flumpy7]

As above. I have one, but after much fiddlement i realised its only good for moving through large quantities of fluid quickly. When it comes to getting rid of those final bits of air you need to bleed properly.

I buy some of that cheap tubing for fish tanks as its slightly smaller than what you get from an auto shop and gives a really tight fit around the nipple. Connect it up to a one-way bleed valve and youre really flyin'.
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[Reid]

Thanks for the advice guys, looks like it's back to using the traditional method after all.

Bezzer: I've actually got one of those cheapo one-way systems (although I'd debate it's one-wayiness ), was just struggling with using it on a dry system so got the Mityvac. Didn't even think of going back to it now I've got most of the system sorted.

Thanks again everyone

[Kickstart]

[Hetzer]

The Mityvac is used only for the initial phase, as Keith says. Soon as you see a decent amount of fluid coming through you have to go back to pumping the lever.
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[Robby]

If you're bleeding after fitting new lines or draining down the system, then don't try to full all of the air out of the bottom of the system. Leave it for an hour, and let the bubbles move to the top of the lines, then just pull the lever back a few mm to let the air up into the master cylinder.

The air pocket in the top of a caliper is really tiny. Most of the air to be displaced after draining the system is in the lines. The lines are very narrow, and air bubbles move up them very, very slowly.

If you try to bleed the whole system through the calipers, all you do is waste fluid. The air bubbles stay at the same place - pushed down the line when you pump the lever, then rising, then being pushed down again.

Bleed the calipers last, a very small amount of air will come out.

[Fizzer Thou]

When I disassembled the six-piston calipers on the Exup last I knew that there would be a problem with bleeding them.So I loosely mounted them onto the forks and after the initial bleeding I removed them from the mounts and inverted them so that any air pockets would move to another point,normally near to the bleed nipple.

When I bleed calipers I use a suitable length of plastic tubing (easily available and cheaper from B&Q) as well as about a 2" length of rubber hose to attach to the nipple.
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