Need help with brakes (new lines/system)

[BruthaMan]

Hey guys,

We're just about finished with the restoration of Pancho and having some trouble with the brakes.

Here's what we have:

1) New brake booster

2) New Master Cylinder

3) New Prop valve

4) New stainless lines front and rear

5) New calipers all the way around

Everything is new on the system with a rear disc brake conversion.

Symptoms:

1) With motor off, we have manually bled, hand pump bled, and power bled with air compressor. After a two pumps, it starts getting stiffer like it should, but can never get it on the first pump. Brake pedal returns normally.

2) More troubling, with the motor running and the booster hooked up to vacuum, pedal goes to the floor quick and then "squishes" back up slowly. No amount of pumping the brakes, WITH the motor running, gets anything at all. Just straight to the floor and slowly comes back up.

Things we have tried:

1) Bench bleed the master cylinder. No problem.

2) Hand bleed, hand pump bleed, power bleed with air compressor based bleeder tool.

3) Recenter the prop valve.

4) Rebleed the system.

The most troubling part is, with the motor running. If we disconnect the vacuum line, it goes back to described above, but the pedal returns normally. With vacuum line on, the system is a no-go. Straight to the floor, slow return on the pedal.

This is a brand new system, new lines, new everything. Spent two days on it so far and even had a bud from Mieneke come out a look at it (before we knew how it reacted with the motor running).

We're missing something, but I'm not sure what it is. Any of these symptoms seem familiar? Sure could use some advice! Once we get the brakes working, will be time for a test drive and you can imagine how eager (after a year of restoring) we are to do a test drive!