1995 Pontiac Grand Am POWER STEERING PRESSURE CAP

There is a press fit cap on the right(passenger) side of the steering rack. This cap was blown out by the hydraulic force in the rack. I removed the metal distribution lines and confirmed there were no blockages in the lines. I also confirmed that there are no blockages in the return hose to the pump reservoir. I replaced the end cap, refilled the system I then started the car, and with the car still on stands, turned the wheels to the left with no problem. Turning the wheels to the right, however, results in the end cap on the rack blowing out and the loss of all system fluid. What could be causing this? Ty