How do you take the power steering pump off a 1989 Chevy Astro van?

Get a 5/8 flare wrench to take off the high pressure hose and a screwdriver to take off the low pressure hose. Drain out fluid. Then you'll have to get a pulley puller to pull off the pulley. Once off the mounting bolts are exposed for you to take off the pump. Be sure to check brackets for cracks as the 89 is prone to this. Mounting is the reverse of this.

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Just a suggestion, I just replaced my power steering pump on a 94 which should be the same. Remove the two piece radiator shroud which improves accessibility. Now you can see what you are doing much better. When you get to the pulley removal part.... leave it on (unless you have a good air supply and 1/2" impact gun) and remove the bolts from the aluminum bracket that goes into the cylinder head. If your pump has a remote reservoir remove the filler hose at the top of the pump. Next remove the two front bolts holding the ac compressor to the aluminum bracket. Slide the bracket down and you can take the whole deal to Advance or Auto Zone and they will gladly remove the pulley and pump and reinstall the new one back on the bracket.