Trouble adding Brake Fluid to System after Rebuild

[mmatches1]

I stripped apart my master cylinder and replaced the parts with a rebuild kit, cleaned the lines and than installed the parts. A while back I removed the disc brakes and replaced the pads. I purchased a vacuum pump from NAPA to draw the fluid through the system. I loosened the bleeding nipple with a tube attached to the vacuum and began drawing fluid through the system. Fluid moves through but mixed with air and the bubbles never bleed out. All along I am adding fluid to the master cylinder keeping the level above the bottom. Am I missing something? Perhaps I am loosening the nipple too much and allowing air to flow in through the thread? The vacuum level on the device says that there is pressure during the process. I have bleed almost an entire bottle of fluid through the system and don't want to try again until I figure this out. Any help would be greatly appreciated. Cheers, Doug

[bikerphil]

The air bubbles you are seeing are most likely being sucked thru the threads of the bleeder screw. If you sucked a bunch of fluid thru, you probably got all the air out of the system and I would ignore those bubbles. If you really want to be sure, wrap teflon tape around the threads of the bleeder screw.

[crazy steve]

...wrap teflon tape around the threads of the bleeder screw.

A big +1 on that. That will not only eliminate the bubbles you're seeing, but make bleeding go faster.

[snakedriver]

I've had this problem too, and I've never thought about teflon tape. Good tip!

[mmatches1]

Ok - thanks. I tested the lever and the brakes appear to hold firm. However, I noticed than the new pads rub on the discs. Can I assume that the pads will wear down/break in after a short ride?

[crazy steve]

A small amount of rubbing can be normal. Yes, you'll need to 'bed' the pads and wear a few high spots off, but as long as the wheel will turn freely it's good.

[mmatches1]

It almost sounds like rubber rubbing but I cannot find any tire contact points. The wheel turns but there is good resistance at this point.

[crazy steve]

Generally speaking, you won't get more than three turns out the front wheel with everything installed and giving it a good spin. Anything over one turn is usually ok.

[sthomag]

I've found that greasing the threads works better than tape. I use disk brake grease from Permatex, because it won't contaminate the brake fluid. A generous smear and no bubbles.

[mmatches1]

Brake grease is a great idea and I will give it a shot. Thanks.

[Courtney]

Brake grease is a great idea and I will give it a shot. Thanks.

Well I used teflon tape yesterday and it worked a treat, along with my mightyvac on the rear brake system. Doing the fronts right now!

[crazy steve]

Teflon tape won't attract dust/dirt.....