Brake pedal going to floor after caliper rebuild

[Rostasteve]

I rebuilt a front caliper and after re-installing it and bleeding the system, the brake pedal falls to the floor and requires several pumps to build up enough pressure to stop. After a few seconds, pressure is gone and I need to do it again. No visible leaks.

What can cause this? air in the lines/caliper? air in the master cylinder? anything else?

Here's what I did:
- took caliper off
- plugged the line to prevent fluid loss. Lost at most 1oz of fluid while doing this.
- rebuilt the caliper -- cleaned internals, new seal and dust boot. Did a rough air pressure to make sure the seal held off the car.
- put the caliper back on, opened the bleed screw, and started bleeding using the 2 person method until fluid flowed from the bleed screw.
- Then hooked up a Motive pressure bleeder and bled the rebuilt caliper for a while.
- Then bled all 4 corners with the pressure bleeder briefly.
- The fluid level in the reservoir NEVER dropped below half full
- Total amount of new fluid pumped was ~500ml (that's all I had)
- Took it for a drive and the pedal is completely soft and requires 2 full pumps to get any braking power.
- There are no visible leaks, no puddles, no decrease in fluid level in the reservoir.

Note: I've replaced calipers and brake lines in the past and never had the pedal be this soft.

Help.

[W Cole]

Sounds like you still have air in there still. I would bleed manually (2 person method) and see if it gets better.

[tlrid3r]

Originally Posted by W Cole

Sounds like you still have air in there still. I would bleed manually (2 person method) and see if it gets better.

Yes I agree. Make sure second person is pressing firmly all the way to floor

[MasterP]

It's more time consuming but I'd do motive pressure bleeder and gravity bleed.

Also, you should try to trigger ABS - you could have air in ABS Unit.

[5soko]

to do a proper bleed your gonna need to use DIS or INPA and activate the ABS system to fully bleed..