Power Steering - small leak and fluid change

[Fitz98]

98 Expedition 5.4. 145K miles
I notice a very slight noise when turning the steering wheel, typical of a power steering grind sound, but faint, with a little bit of a "chop" in the steering wheel when turning wheels to the left at a stop, like the start of a turn, then a small jump or skip, then the faint grind sound.
Under the vehicle, I notice some evidence of fluid stains on the steering box (no drips, just a residual discoloration). Hoses seem to look fine and the level in the resevoir remains full.
Since I have changed all other fluids, I thought I might change the power steering fluid as well.
1) Should I add any P/S leak repair, if so to the fresh fluid or old fluid before the flush
2) How do you flush the P/S system?
3) What does my description sound like to you people with experience? (I had a lot of great advice for my transmission fluid change in this forum)
4) I understand that the P/S system uses the same fluid as the transmission. I used Valvoline MaxLife Dex/Merc in my transmission. Is that what I should use in the P/S as well?

 

[wallyuwl]

Don't add any leak repair. You can just use a suction gun and take the fluid out of the resivoire. Do this three or four times, each time one week apart. You should have almost all new fluid after this. MaxLife should be fine to use (not 100% sure of the effect of the seal conditioners in the PS system), though to be totally safe you could just use the specific transmission fluid (presumably Dex III). You may also consider filling with lubeGard purple bottle power steering protectant on the final fill. When I did mine I called LG just to make sure this was compatable with the transmission fluid in the PS system, and they affirmed it was.

 

[tinmanSC]

1) Never use any stop-leak type thing unless recommended by the manufacturer.
2) To flush the system you find the return hose (the hose that returns the fluid from the rack to the reservoir). With the engine off, disconnect that hose, and while adding fluid to the reservoir turn the wheel right to left until clean fluid comes out. Best to jack up the wheels to do this. Or you can take a turkey baster and just suck the fluid out, add new... turn wheel... suck out old fluid... add new... etc... until you see only new fluid. Most P/S systems hold about a quart.
3) Does this sound like the steering rack could be moving or is it just a pump type sound? Sometimes bushings and such get old and when you turn the wheel the rack moves a little. This can cause all kinds of odd feelings for the driver. Mostly regret and impending doom.
4) MaxLife works great. It's a good Dex-III fluid, don't let the "MaxLife" fool you. Perfectly safe for the P/S system.

 

[BoomerCTD]

Agree with the above recommendations, except I would use Mercon V fluid for that ford.

 

[OVERKILL]

Mobil 1 synthetic ATF. Grab two litres of it.

Use the method tinmanSC described.

How I did it:

1. Rig a "bucket" underneath the PS reservoir.
2. Remove return line, let old fluid drain into bucket.
3. Cap the return line nipple in the bottom of the PS reservoir.
4. Put the return line in the bucket.
5. Fill the PS reservoir with new fluid
6. Have somebody start the vehicle and work the vehicle lock-to-lock while you dump new fluid into the reservoir to keep it at a safe level.
7. The fluid coming out the return should change colour.
8. Stop (shut off the vehicle). Hook your return line back up.
9. Top up the reservoir.
10. Restart the vehicle, check for leaks, go lock-to-lock a few times again. Shut off the vehicle. Check the level in the reservoir again.

 

[Fitz98]

Worked great, easy job. Thanks to all.
Used Valvoline MaxLife Merc/Dex Synthetic. Same as I used in transmission.
P/S system is behaving well now. Old fluid was pretty burnt smelling.