parking brakes on 1986 f700

[bladerunner]

I recently rebuilt all wheel cylinders on my f700. It also has hydraulic parking brakes that worked well before I rebuilt the brake cylinders. The brake pedal seems not to want to stay up. It works but you have to at least pump it one time. The parking brake will not hold with a load bigger than the trucks actual weight of 10K. Is there a way to adjust this? I have been told they had an AB valve on these types of units and to change it out if the parking brake did not work. I have yet to identify this AB valve. I have bled the regular brake system but have not been able to bled the hydraulic parking brake yet!.Anybody got any suggestions?

have a nice day

Bladerunner

[48prerunner]

Are you taking about the parking brake where you have a electric toggle switch youturn on then you hit the brake pedal to set it? Sorry can't think of the name right this second? Works like a line lock we had them on the trucks without air brakes.