Hello. I recently acquired a 94 f700 with a 5.9 Cummins and the hydromax brake system. I had read some diagram info on how the system works that Subford had posted. The issue is when the parking brake is released the pedal pulses about once every second. It doesn't pulse with the park brake applied. I can feel it pulsing on my foot and can see the feed line to the HR-1 jump everytime it does it. The brakes work fine and there are no buzzers or dash lights coming on from it but I don't want to have something fail with it constantly doing that, just trying to track down the procedure to know for sure if the hr-1 bank is bad or something simple like an o ring I am missing? Thanks in advance!