Here are tips on how to bleed a new master cylinder from a real pro .. Van, of Vanco Power Brake Supply in California .....
If you will bench bleed the MC, then follow his simple bleeding instructions once you have it installed, you are home free ...
(from my HydroBooster instructions page at
Bench Bleeding the Master Cylinder:
Put the master cylinder in a vice.
(It won't hurt to point the piston end downwards a little)
Fill both reservoirs ¾ full with DOT 3 brake fluid.
Using a screwdriver - push the piston in ¾ way, plug both output holes with your fingers and release.
WARNING - DO NOT OVER-DEPRESS THE PISTON!
Do this until fluid streams out of both lines.
When done, put the plugs back in the ports.
Mount the master cylinder to your firewall.
Brake Line Bleeding:
1. Get a helper to jump in the Jeep and work the petal.
2. Back off the master cylinder's brake lines one turn (both of them).
3. Have your helper push the brake pedal to the floor.
4. Tighten both brake lines and have the helper release the brake.
Repeat 2-4 until the fluid streams out of both ports without "sputtering".
THAT'S IT! Your lower brake lines will usually not have to be blead since this simple operation evacuates all the air in the upper lines.
It's exactly like bleeding the slave clyinders or calipers, only you open both fittings on the MC at the same time instead.
P.S. You might want to get a price quote from them on a new MC.
He and his brother are real nice guys. (323) 563-1588
He never recomends using even a re-manufactured one.
Your life depends on it!
They DO, however, re-man Jeep porportioning valves for $75 bucks.