hard steering/loss of power steering

[3nissans]

fellas:our 1998 frontier, which the daughter uses daily, develop this problem with the steering. it is really stiff when turning at really low speed as in pulling in and out of the garage/parking spot. sometimes, it does the same thing on round abouts doing about 15 mph. i've replaced the power steering pump and it's still doing the same thing. I wonder if the remanufactured ps pump I got is also bad or could it something else. Is there a way of checking each steering system component to pinpoint the problem? thanks in advance.Denny

[Florida240sx]

Sounds like air in the system. Leaking anywhere?