Pedal brake bleeding with safety valve

[bc3j]

I have a 1970 Challenger RT with the disc brake valving that was used starting after January 1, 1970. I've always used a pneumatic system with an air compressor to bleed the brakes. If I would use the pedal push, hold, release method would the safety switch move off center as if there was a failure in the brake line? The last car I bled the brakes that way was with the old single master cylinder. Thanks.

[1 Wild R/T]

If you bleed a system that the pedal hasn't been traveling far in the bore & you suddenly push it through it's full travel you'll likely damage the seals & have a sinking pedal after that...  Tear apart any old brake system & you'll find crud deposited in the M/C W/C & Caliper bores... And you can bet theres more of the same in the lines & valves... Flushing/bleeding helps but the M/C often gets damaged cause suddenly your pushing the seal into the crud & the seal lip gets damaged...

Pressure bleed, vacuum bleed or gravity bleed...  Or plan on taking the M/C apart to clean it before you bleed the brakes....  Or gamble, you might get lucky....

[bc3j]

Thanks. All brake components are new. Just was curious if I pedal bleed and open a bleeder if the safety switch would go off center and close the opened line as if it failed.

[1 Wild R/T]

The safety switch/shuttle valve on a Mopar is self centering, you can bleed past it but if you apply the brakes and one side of the system doesn't hold pressure the valve shifts blocking fluid to that side..  When you lift off the pedal the valve self centers so you can bleed as long as you don't stomp the pedal & cause the valve to shift... Again, if you do stomp when you lift it will self center & you can go back to bleeding but be a little less aggressive about if....

[bc3j]

Thanks for the info.  Wasn't sure about it. 

[MoparLeo]

An old time way of preventing damage to the master cylinder from pushing the pedal down too far when bleeding was to put a block of wood between the pedal and the floor. You can't damage the m/c seals by pushing the piston in too far that way.. Safer to just gravity bleed if you don't have a vacuum bleeder.