Originally Posted by Max Headflow

I suspect that while not described right, one issue allows air to be trapped in the master cylinder. It occurs in the area between the rubber cup and the seal that keeps fluid from dribbling out where the pushrod goes in.. If air gets trapped there, using the brake will allow the air to bypass the rubber cup and get into the pressure side.. The master reservoir has 2 holes that feed the brake plunger. The one closest the lever is the main feed. The smaller one is on the pressure side of the cup to bleed off pressure as the brakes get used and the calipers / fluid heats up..

If the plunger has some air trapped, one way to get air out is to crack bleed fitting, pull the lever all the way to the bar and tie down with rubber band. This pushes the rubber cup past the small hole and allows trapped air to work its way out into the reservoir..

Another way to get rid of the bubble is simply position the master so that it's flat and work the lever a little. This will allow the air to bubble out through the bigger feed hole.

Getting the air out is a common issue on brake masters if they are not held reasonably flat while bleeding the brakes..

Originally Posted by snake_eyes

Which bleed fitting are you talking about?

Originally Posted by Max Headflow

Either one on the calipers.. The main purpose for opening it is to simply get the lever to the grip then hold it there and close the bleeder. While doing this, do not release lever, tie it down.

Originally Posted by snake_eyes

Thinking about spending some quality garage time this afternoon, I'll give it a shot/

Originally Posted by WP50

I can tell ya from past experience it is worth a shot sir

WP

Originally Posted by John CC

It's 9 degrees F in the garage today...

Originally Posted by John CC

OK. I thought you were trying to say air in the lines would get back to the reservoir. For that, the lever has to be completely released.

Originally Posted by WP50

I can tell ya from past experience it is worth a shot sir

WP