The service manual is vague and recommends a very complicated way of doing this, and I couldn't find any good walkthroughs for Subaru's. At 115k, my power steering fluid was black/brown and full of some particulates. At full lock it the accessory belt used to complain despite being new and adequately tightened, this no longer happens. Here is a better way, it can be done in 15 minutes and without getting under the car or unbolting the subframe braces.
You will need at least 1 qt of oil to do this. I used some left over Valvoline ATF to flush before I repeated the procedure with 1 qt Mobil 1 Synthetic ATF Dexron III.
1. Loosen/remove front accessory belt so you can turn the power steering pump with your finger. Since most of us don't have a belt tension tool, you can mark the thread of the tensioner bolt (on the top side) or feel the deflection by hand and match this for when you put it back on.
2. Jack up the front of the car at the center jack point so that the tires are just off the ground and the steering wheel can be turned freely with the engine off.
3. Pull the top hard line (return line) from the power steering fluid reservoir (On the GT this has some aluminum fins for cooling), this will allow you turn it towards the front and place a catch pan for the oil fluid underneath it.
4. Turn the power steering pump by hand, clockwise. Dirty fluid will come out of the return line. Keep turning it until the reservoir is basically empty and you can add new fluid. Try not to completely empty it, however it's not the end of the world if you do, as it will self bleed, and this procedure in itself will bleed air out of the system.
5. Add new fluid to the reservoir all the way to the top (past max). Repeat step 4 until new clean fluid comes out of the the return line.
6. Put the key in and turn it so the steering wheel is unlocked, but DO NOT START the engine.
7. Ensuring that you keep the reservoir full, turn the steering wheel from lock to lock using slow consistent pressure, taking several seconds to do so. Fluid will be pushed out of the rack and into your catch pan. A full reservoir is good for at least one full lock-lock. The fluid coming out will turn back to old fluid and then back to new.
8. Having gone from lock to lock at least once to left and once right, repeat the last step until no old fluid is expelled, once this happens, ensure you leave the reservoir at "COLD MAX" either by adding and removing fluid via turning the pump.
9. Put the return line and accessory belt back on.
Check the reservoir level after the next few drives. If you got air into the lines, it will drop, so top it off again.
Last edited by Deer Killer; 10-27-2011 at 03:04 PM..