I'm having a problem with my power steering on my 95 Sentra GXE. It intermittently reduces power assist and the pump is whining while I turn the wheel. I pulled a used rack this week at the junkyard ( $25 ) from a low mileage car ( the original one has a small leak) but was wondering if it could also require a pump as well? How do you tell if the problem is with the pump or the rack? It does have full PS fluid and I changed it to a synthetic PS fluid in the last 30k miles.