Master cylinder / line lock bench bleed

[findog78]

Just added rear discs to my 69 C10, new master, 4 caliper prop valve, and a line lock. My question is do I bench bleed with the prop valve and the line lock at once, or the master cylinder only?

[PbFut]

The master has a fair amount of void to fill, so bench bleed is recommended, but not a must. If you are confident you can get the air out of the other components then just bleed those after install. Be sure to have a lock tool for the shuttle valve or you will lock out the rears and not get all the air out and chase your tail for days. FYI, the area the brake switch threads into is the location you tread the lock tool into. It is isolated from the front and rear circuit so you don't have issue with removing the tool and replacing the switch after everything is bled.

[findog78]

Just ordered the Valve Bleeder Tool. Thanks!

[vics stuff]

I just did my brakes and did not use the tool for the shuttle valve. Everything went well. After a few days of driving I did notice that I got a brake light indication on the dash. I think the shuttle moved and now I have to go back and fix this . GRRRR!
Vic

[PbFut]

Some say you do not need the tool. I think it may be those who are bleeding older systems with tight or even stuck shuttle vavles or they don't realize their rears are locked out and the 50 year old brake light or switch has failed. My experience, admittedly limited to hobby use, is that the shuttle valves in the presently available brake valve moves very easily and will lock out the "bad" circuit quickly. Even a curcuit with too much air will trip the valve. So you can never properly bleed without the tool since the circuit you need to bleed keeps locking out.

[70STOVEBOLT]

I thought you were supposed to use a tool to hold the button in on the front of the combo valve when bleeding? That is what the GM Chassis Manual shows.