[blaktopr]

Jeep Grand Cherokee steering box swap in 72 Lemans with Cardone reman pump in original case. New lines, fluid, bled to death on lift, and even added treatment. Basically normal driving no higher than 2500 cruise system quiet all day. Get on the highway, merge with heavy throttle into traffic then cruising at about 3k for a few miles, the system starts to whine a little. Steering works fine just noise. I tested the pump/fluid with temp gun and hottest part is at face of pump at 195 degrees. Fluid under cap 170. Start car back up and drive down road and noise starts to go away. Run errands,, stops etc,, and quiet.. Seems temp related but 200 is common under hoods these days.

[77 TRASHCAN]

What brand od additive? I've used Lucas brand PS additive, seems to be good stuff.

[chuckies76ta]

I would think you p/s pump whine is coming from the temperature of the fluid. I've never seem any p/s with fluid that hot. Gotta remember this p/s pump is just moving your steering, unless you have other equipment connected like a hydra-boost. You can also install a small cooler on it.
I just googled p/s pump temp and the consensus is like 180*-200* is not uncommon. The temp with my hydro-boost did get hotter than what I though was normal, so I installed a cooler on it. It's been fine since installed 10 years ago.

[steve25]

I use to have a Subaru that had a slow fluid leak.
I would know it was time to add fluid with the first start up in morning after it got too low.
Only then would it whine and and have no assist ( cool fluid = less volume ) after turning the wheel a certain amount .

If your getting whine when it’s full then as posted it must be due to loosing pump efficiency from the fluid getting too hot.

Are you running different size pulleys and driving the pump faster then needed?

That will build up fluid heat faster.