well sounds like a bad power steering assist module(basically a relay), remind me tommorrow and I look it up and check location for you......you know that thing about age and memory......and time

 

sorry, yes I did and I was thinking of the XK, you dont have it...so recommendations...is this something new to the car or always seemed this way? Check belt tension, obviously if a little too loose it will reduce performance of the pump and lower rpm and speed. Then youde have to run a system pressure test to see what the pressures are, but even we dont have the gauges for this

 

This pump is the reverse pressure type, the slower it turns, the higher the pressure is supposed to be. I think your pump is shot and just too worn to put out the pressure at low speed. The only way to know is to get the pressure checked or just replace it. The module isabove the left side valence panel where the brake switch wiring goes. You may need Alldata.com to find it as it is not very big and it is not marked. As Brutal said, it could be the module (and easy to change), but I would bet on the pump. You might check the relay as well and be sure it is not this.

 

Let us know how it goes. I'm always keen to keeping an eye open for future problems and how to fix 'em!