Brakes: Bench Bleeed Master Cylinder

[dangrdan]

Howdy,
When I bench bleed the MC on my 66 Daytona w/power brakes, using a socket extension to push back and forth, I get to the point when all air bubbles are removed. However, when I release all pressure on the MC plunger piston, the plunger spring pushes the piston back at the end of the stroke beyond the fluid opening, which sucks air back into the MC. I suspect you are supposed to hold the shaft until you fit it onto the brake booster shaft and then mounting it back onto the booster without sucking air back in. Unfortunately, the booster shaft is on an in-stroke so it does not extend out enough to meet the MC plunger shaft, thus air is drawn back I try to reinstall the MC onto the booster. I can't pull the booster shaft out easily; I am afraid to put too much tension on it (pulling) for fear of screwing up the internals.

I am hoping to get the engine running next week. My plan, unless some of you have a better idea, is to push on the brake pedal after the engine is running, which I expect will cause the booster shaft to extend far enough to meet the MC plunger. When the booster is fully extended, I would then re-bleed the MC and maybe get it onto the booster shaft without drawing air back in. The MC was removed several years ago and I cannot remember how far the booster shaft extends. Or, maybe it is really okay to just forcefully pull the booster shaft out without running the engine? That would mean I could get the brakes finished this weekend.
The manual gives no guidance on this so any help you have would be much appreciated.
Dangerous

[52 Ragtop]

Try here:

http://www.superchevy.com/how-to/brakes/0509sc-bench/

Jim

[TWChamp]

I hold my fingers over the openings when pump the master cylinder piston untill the air is out. I have a couple fittings I can screw into the hole to keep any fluid from leaking out while I install the master. Once installed, just unscrew the blank off fitting and screw the line in. Whis has worked fine for me. If you have a helper to push the pedal, you could loosen the line at the master while he pushes the pedal just to be sure the air is out.

[bezhawk]

Just leave the bench bleed set-up in place while you bolt up the master cylinder to the booster. As long as there is a bleed tube submersed into fluid, air cannot be sucked back in. Then once in place the regular brake lines can be installed.