For some unknown reason Toyota engineers decided to put a fine mesh screen inside the power steering reservoir. When the screen clogs up, as is common on a 20+ year old system, the result is cavitation at the power steering pump. Cavitation will make the pump noisy and / or the steering jerky............especially when the van is cold. The best way of fixing this is to flush the system, clean the filter, and put fresh fluid back into the system.
I'm not sure what the factory recommended procedure would be for this, but as long as you get the old out, clean the filter / screen inside the reservoir, and refill with new fluid you should be in good shape. I empty the system by pulling a pressure line from the rack, then start the motor and use the pump to spray it into a bucket or drip pan (warning this can be messy). After it's all out, you may wish to put a quart of new fluid in the reservoir just to rinse things out. Leave your drip pan in place and let the new fluid puke out like you did with the old. Don't worry about letting the system run dry (it won't hurt anything).
The tough part in all of this is cleaning the screen /filter inside the PS reservoir. IMO Toyota was not thinking straight when they put that thing inside a reservoir that was not designed to be taken apart. It can be taken apart and cleaned, but since it involves bending metal tabs, you're probably only going to get away with it once or twice before another reservoir would be needed.
Here are some pics of a reservoir I took apart for cleaning of the screen / filter.
It's tough at 1st to unbend these tabs. I used a 90 deg scribe from the side to get them started. It takes some force and some patience, but once you get it to this point a large slot tip screwdriver will finish the job with ease.
This particular reservoir came from a salvage yard and sat around dry for a while. Yours will probably look a little different inside.
I used a big bucket and some mineral spirits paint thinner to clean. I poured the paint thinner in the bucket, then threw the parts in and sloshed it around. I took the parts out and blew dry with compressed air. I ended up putting the reservoir back in the solvent/thinner and I repeated rinsing/drying until I was satisfied with the results. That spot you see is a stain on the bottom of the reservoir (not junk on the screen).
Re-crimping the reservoir lid.
All ready to be installed.
When it comes to filling back up, Toyota calls for Dexron II (which is NLA), so Dexron III is the next best choice. Stay away form the newer Dexron fluids (like Dexron VI) as they are synthetic and may or may not be compatible. This is a recirculating system and is also self priming / self purging. This is nice because there is no need for any special care when refilling or servicing. Once the pressure line is hooked back up just start the engine and start filling the reservoir. The pump will suck the ATF easily. Pause every few moments and listen. When the pump stays quiet without you pouring, shut off the engine and top off using the dip stick inside the cap. Start the van again, turn your steering wheel from stop to stop (to get any errant air bubbles), shut off and recheck fluid level. Add more fluid if required and you're done!
If you are cheap and lazy, and only care about shutting up that noisy pump, an alternative way (short-cut) could be to forget about everything I just said and simply poke holes in the reservoir screen with a screw-driver. Of course this is defeating the purpose of the screen and you would be releasing all the grit previously captured back into the system. This method would also most likely shorten the life of your power steering system. Have fun. Tim
PS: Since you're servicing your power steering system anyhow, it might be a good idea to check the pump for leaks and repair (if required). Here's a couple of good threads on that:
http://www.toyotavantech.com/forum/s...-Steering-Leak
http://www.toyotavantech.com/forum/s...alot-of-fluid!
https://www.toyotavantech.com/forum/...-steering-pump