P/S whine issue and hydro boost question

[sd73man44]

I have a '99 7.3l F250 and have been having some p/s pump whine on occasion that has been hard to do the diagnosis.

First I thought the pump was going south but now I am not sure there is any problem with the pump.
I noticed a slight fluid leak on one of the lines coming from the hydro brake boost unit down to the p/s gear box. My fluid loss was very minimal in the CII resorvior. I could only add about an oz of fluid and it would stop the whine.
The truck is a '99 so I replaced three of the p/s lines (they were pretty rusted and it was time to change them out).
Some times when I tap the brake in a parking maneuver I get feedback and whine from the p/s.
I could have air in the lines but my real question is "Do the Hydro Boost Cylinders sometimes develop a small leak?(internally) and weep a small amount of p/s fluid. When I R/R the p/s lines I never actually found any holes in the old lines but they were rusted badly and like I said it was time to change them out.

[robertth]

Both times mine started whining, changing the P/S fluid with ~4 quarts of Chevron Delo MD-3 fixed the problem. I would assume it is not the pump and if you haven't changed the fluid in the last >60k miles, that will probably fix the problem. There is a procedure on the TDS somewhere that tells you how to do it. Use a turkey baster to get as much out of the reservoir first. Some people lift the front end of the truck so there is no pressure on the tires when you move the steering wheel, but I have just done it on a gravel surface with cardboard under the tires so as to minimize the friction and tire wear. Keep the reservoir full (very important) as you turn the wheels and pump the brakes.

[01f25073]

Try a power steering system flush and see how your system is behaving. Here is a link on a "how to" video

How To: Power Steering Flush on 7.3L Powerstroke (HydroBoost) - YouTube

How To: Power Steering Flush on 7.3L Powerstroke (HydroBoost) - YouTube

Thanks to Trey!