brake bleeding question

[speedman]

I am getting air bubbles in the bleeding tube line running from my caliper to my mitivac hand pump. I think it is coming from air being sucked in around the bleeder screw threads. I was thinking of removing the bleeder screw and coating it with Vaselines on the threads to see if this would help. Does anyone have any suggestions. Thanks!

[Bob Kontak]

Air can be sucked into the hose where it meets bleeder screws. It wont hurt a thing. If you are fussy you can get a tighter fitting hose.

[gtc]

Do you have someone to press the brake pedal for you? If you've already flushed the system with the mityvac it should only take one or two depressions of the brake pedal to verify that the lines are free of air.

[aston@ultrasw.c]

the air is likely being pulled through the threads, you can try some teflon tape

[James Brown]

Perfectly normal, keep the suction going when you close the bleeders and it will be fine.

[911pcars]

It's best to use positive pressure, not vacuum, to bleed air out of a hydraulic system. If you attach a length of clear hose (about 1/4" ID) onto the end of the bleeder screw, then open it, atmospheric pressure will be enough to force fluid and air out of the system, even past loose bleeder screw threads.

A pressure bleeder will increase the volume of fluid through the system.

Sherwood

[tabasco]

On the other hand, a vacuum bleeder makes the air bubbles bigger, so they're more likely to move from where they are stuck. A pressure bleeder makes them smaller.

To put the teflon : have someone press the brake pedal, it will close the system. Then you can remove the bleeder screw and you won't loose too much fluid. Put teflon tape.
Then you won't get bubbles anymore.
Without teflon, my mytivac would not get much fluid, mostly air.

I have both, I use the pressure bleeder on the Porsches as it works fine, and I use the Mytivac on the cars where the pressure bleeder does not fit easily. I like both.

-Guillaume