Its about that time, for me to flush all the gunk out of the radiator on my 91 gxl...

What is the best method to clean out the coolant system? Drain, fill with water, run, drain; repeat?
Could someone clarify on what i should do, and a good coolant to use.

I bought some 50/50 Havoline stuff from walmart.

+Brad

 

The factory service manual will tell you what to do. It is under the How-To's menu.
http://fc3s.org/

You can flush it out with a garden hose, but fill it with distilled water (about $.80/gal at the supermarket) when you add the coolant.

There is a big debate about using the "orange stuff" in the RX-7. I don't really know, so I stick with the "green stuff".
http://www.scuderiaciriani.com/rx7/cooling.html#ANT

 

This is what I do:
Buy a can of radiator flush. Follow the instructions, but with most you dump the stuff into the radiator and idle the engine for about 10-15min after the engine reaches operating temp. Don't forget to have the heater set to hot the whole time. Once the engine's cool enough, remove both the radiator cap and the cap on the engine (by the thermostat housing), drain the radiator using the tap at the bottom, then remove the engine drain at the bottom of the centre plate on the LHS to drain the block. Now stick a hose into the radiator neck and turn it on. You might want to stuff rags around it so it doesn't just overflow. Do this until it runs nice and clear, then repeat this using the filler by the thermostat housing (to flush the engine). Now reinstall the engine drain and close the radiator tap. Open the breather vent on the radiator neck (if you have one) and refill the engine with a 50/50 mix of quality coolant and water. Reinstall the breather and cap on the engine and start the engine. As the engine heats up keep topping up the radiator as required. When it full and no bubbles are appearing, put the radiator cap on and you're done!