Need to replace the master cylinder in my 74 and want to bench bleed the new master cylinder.  Cant seem to find any plugs that will fit the line ports.  The Bendix instruction says that "fill and when the fluid begins to drip from the outlet ports securely install threaded plugs.  This provides lubrication to the piston seals before bleeding".  Anyone have any idea of the plug size for the ports?  Tube size is 3/16" on the front and 1/4" on the back but standard plugs for that size don't fit it.

 

 

The thread sizes will be pipe thread, so a normal plug will not work. Also, the "plug" would have to have a flared type seat to fit, and seal.
The best way to do this, is get a set of fittings/hoses for this. You can get them at any parts house, and most reman cylinders come with them. Go to AutoZone, Pep-girls, etc, and see if they have one of those "Help" sections. You will find a kit there for bleeding the master. They are really cheap, and you can save it for later, and loan it out to friends. It comes with several plastic/nylon fittings, and hoses for bleeding the master.

Thanks Joel, I'll check out my local Advance Auto/NAPA/etc.

 

I just did mine a while ago as the rear seal let go and had no back brakes.  My MS came with a bench bleeding kit included.  I'm pretty sure it originally came from GM direct or possibly Ecklers (I bought it from an importer in Oz. Cheaper).  Easy to do, just clamp the MS in a vice and fit the rubber plugs to the outlets and feed the plastice hoses on the rubber plugs back up into the top of the MS into the brake fluid and GENTLY pump the MS with a rod.  Once the air stops going through the hoses you're done.

Don't forget to put the blanking plugs into the outlets once you've removed the rubber tubes.

If you have someone to push the master cylinder, you can just put your fingers over the outlets, and use them as bleeder screws.  No need for a kit.   Granted its a bit messier, but works well.

Went back up to Advance Auto and they rooted thru some boxes till they found two plugs that fit.  MC is bled and in.  Bled each wheel and noticed that the rear brakes have two bleeders.  Took no chances and bled both of them on each side.  As much as she hates it, Miss Ruby now stops.