What do you do, suck out fluid from resivour and unscrew that big plug from the rack and pinion unit and drain it from there?

 

Just undo both lines off the steering box. Not completely mind you; just enough for them to leak into a drip pan. have some coffee or beer while it drains. When it stops just tighten the fittings and re-fill with fresh. Clean up up with engine degreaser.

 

How often should this be done?

 

He doesn't have a steering box. It has been a long time since I have seen the rack & pinion setup. I would jack the front tires off the ground, find the most accessible and lowest steering line and remove it, the big plug may work I'm sure somebody will chime in. Once it has drained I would turn the wheels back and forth a few times. Hook it back up - fill the reservoir, turn the wheels back and forth again a few times. Turn the engine on for a minute or so and let it sit for a while and top off the reservoir again.

 

It's more of a let the pump move the old fluid into a tub while pouring in new fluid type of job.

Here is a write up for a landcruiser, but the same principles apply

http://forum.ih8mud.com/80-series-te...ing-fluid.html

 

Search next time, please.

https://www.yotatech.com/forums/f2/3...ng-post-81347/