My power steering pump in my 05 Explorer 4.6L V8 is starting to howl it's displeasure on a cold start at near zero temperature.
It doesn't do it when warm.
I thought I would change the fluid but the owners manual says to use Mercon ATF, but Ford now sells Mercon V as power steering fluid. It also warns not to mix the two kinds.
So, which one should I use?
And, which way to change it, siphon pump the reservoir and replace with new a few times, or let the pump pump it out and replace as it goes?
Thanks.

 

You should still be able to find the older Mercon fluid at auto parts stores. I can get it at the local Napa. Usually, the later stuff can replace the earlier stuff, but I stick with what was recommended at the time. Why? Because I'm (overly) paranoid.

I used to do the fluid change by sucking out what's in the reservoir with one of those oil suction guns and replacing with new fluid. Then drive it for a few minutes to cycle the fluid through and repeating a few times.

What I do now is to jack up the front end. Disconnect the fuel cutoff switch or pull the fuel pump fuse and start the engine until it won't run, or disconnect the cutoff switch/fuse while the engine is running and let it die. Suck out what's in the reservoir. Remove the return line hose and insert a piece of 5 ft. or so polyethylene tubing (or connect a long piece of PS hose with a union) and run that to a bucket to collect the used fluid. Then, fill the reservoir up completely and have your lovely assistant (blond, brunette or redhead, your choice) crank the engine and turn the steering wheel slowly while you fill the reservoir to replace the fluid that is coming out the return line. You might have to stop cranking periodically so you can catch up with the fluid. I've found that it pumps out faster than I can keep up, especially if the engine is running. You don't want to crank the starter for an excessive period of time as it's not rated for continuous duty. If you wanted to take it easy on the starter, you could remove the plugs, but I've never done that. Once fluid comes out clean, hook everything back up except the cutoff switch/fuel pump fuse, fill the reservoir, crank the engine and turn the wheel lock-to-lock to bleed the air. Keep an eye on the reservoir level so you don't get air in the system. Then, connect the fuel pump disconnect switch/fuse, start the engine and run lock-to-lock for a final bleed before you put the front wheels back on the ground.

That's what I do. It can be messy. Others may have a better procedure. If you have a remote reservoir with a hose that goes to the pump inlet, then you could connect a big funnel or jug that holds a couple quarts to the pump inlet line at the reservoir connection and do the flush with the engine running. However, I would still bleed the air from the system with the front wheels off the ground once I hooked everything back up.

I noticed that your Explorer is much newer than what I drive, so pulling the fuel pump cutoff switch or fuel pump fuse to kill the engine may set some codes.

 

There are no issues from mixing the too. I have been using Mercon V in my systems for years, work great and helps quiet things down.