'68 Z28 Redoing my brakes - bleeders on the MC?

[barsteel]

Hello -

I'm starting the brake system redo on my '68 Z28.  I'm going with new lines, hoses, wheels cylinders, rear shoes and hardware, and a correctly date coded booster and correct master cylinder.

The correct MC has bleeders on the body.  I realize that these bleeders are there to help eliminate any air trapped in the MC due to the upward angle of the booster mount.

My question is this - on every brake system overhaul I've ever done, I've always bench bled the MC...filled it up with fluid, and either blocked off the line ports or routed lines back into the reservoir, then pumped the MC piston until there were no more air bubbles in the lines or coming out of the ports in the reservoir.

Wouldn't bench bleeding before installation eliminate the need to use the bleeder ports on the MC?  If not, how would air get into the MC after the bench bleed, assuming I keep the reservoir full enough to cover the ports during installation?

If I can avoid spilling paint-eating DOT 3 fluid all over my newly semi-gloss painted MC, I'd like to do so.

Thanks in advance...

Chris

[dannystarr]

I am doing the same exact thing on my '68 Z/28 tonight at 5pm.
 Doesn't air get into the lines during the changeover? The old master is pulled, and the lines are sitting there open, hanging there waiting for the new master. No way to keep ALL the fluid in during the swap. Going to be a small area void of fluid at edge of lines. Which in turn ends up being air in that spot. So then you would use those bleeders to release that small amount and you are good. No bleed out thru the whole system. Course you have to do that anyway cause you are doing cylinders etc. I am sure some one will chime in with triple my knowledge   ... Danny

[Stingr69]

The bleeder ports on the MC are only for use on the factory production line.  Not in service. 

You actually allow air to enter the system when you remove the temporary bleeder lines/plugs from the MC. Once the master cylinder and brake lines on the car are assembled, you have to then bleed that tiny amount of air you let in by pushing the bubbles all the way through the lines out to the calipers/wheel cylinders.  Messy and can eat paint.

Just a thought - DOT 5 will not eat paint and does not absorb moisture.   If you are replacing all the old rubber items in the hydraulic brake system, now would be a great time to do the swap. Regular brake system flushes and corrosion will be a thing of the past.  I have done it to all my classics and never had to touch them again.

[dannystarr]

I also installed my original calipers back on. So need to bleed it all out anyway. Good to know on the Bleeders... D