Front brakes give out during brake torque

[fasterthanu]

I replaced calipers all around, the system has NO air in it, and have now installed a vacuume pump for the powerbooster with a canister attached. If I go to brake torque it, even if I slowly do it, the front wheels will give out and turn. WTF. They seem to hold longer if I floor it, but will ultimately turn. Why?

 

[69MyWay]

What happens if you do a quick double pump? Will they bite then?

Sounds like a defective master cylinder.

 

[fasterthanu]

actually, it's a brand new master cylinder. Umm... Quick double pump of the brakes? I will try it today and let you know.