I know this won't be considered a flush, but can you just suck out the old fluid from the reservoir and then replace the fluid?
Of course you can, but yes, its NOT a flush or even a full draining of the system, you likely get a 1/4-1/3 of the fluid doing it this way. Its better than doing nothing at all, some fresh fluid mixed with the old will boost the protection for the system, but yes, NOT as much if you changed all the fluid.
What I do:
**Do NOT start the engine anytime during this procedure**
1.) Put the front up on jackstand so the front wheels hang and can turn full lock to lock without resistance.
2.) Drain the reservoir using a bulb/turkey baster as much as possible.
3.) Disconnect the return line to the reservoir, its the smaller line spring clamped to the reservoir. Run the line to a bucket under the vehicle, use an extension hose, or I just rested the empty jug on a box so it would reach the return line hanging down.
4.) Turn the Steering wheel from lock to lock as quickly as you can, this will circulate the fluid through the entire system, sucking it through the pump, and pumping it out through the return line into the bucket, as the fluid level gets low, it will sputter and spurt out and turning the steering wheel faster will help to squirt out the last of the fluid.
5.) Cap off the opening in the reservoir for the return line (or have a helper hold their finger over the opening). Add a couple ounces of fresh fluid, and repeat the procedure to pump out the fresh fluid, that will flush out any of the old fluid still remaining.
6.) Reconnect the return line, fill the reservoir, turn the steering wheel lock to lock to work out all the air. Keep checking fluid level and working the steering wheel back and forth until the fluid level is no longer dropping.
7.) Lower the vehicle off the Jack Stands.
**Any hydraulic system (and PS is a hydraulic system) that has air in it, can "Hard Over" i.e. extend to one extreme or the other at extreme speed and force. This is extremely unlikely with PS, but be wise and keep your limbs away from the front wheels and steering wheel as you start the motor for the first time.**
8.) Take it for a test drive, make sure to do several turns where you turn the wheel all the way one direction and then the other. Do some Figure 8's. Check the fluid level after the test drive and adjust if necessary, check again 50 or 60 miles later, and adjust the fluid level if necessary.
I was able to do the whole thing, including the flush, plus spill a little and even over fill a few onces and have to suck it out with 1 quart of fluid.
Use the recommended MS-10383 (I have NOT found any other fluid that states they meet this spec, and its a new spec that is required by our Commanders, and few other Jeeps
) only available from the dealer. My local dealer wanted $15 a quart, others may want as much as $20-$30.