I have a 92 accord lx and it appears that the thermostat is stuck closed, so im planning on replacing it myself rather than take it to the shop. I was wondering, is it necessary to drain the coolant in order to replace the thermostat? If this is the case im planning on flushing the system to clear it out and i was wondering how exactly i would do that? I've looked it up elsewhere but couldn't find clear instructions.

-thank you

 

You can drain the radiator, then when the T-stat is out stick a garden hose in that hole, and let it run full flow for about 5 minutes.
leave the temp setting on full heat to open up the heater core valve.
The head and heater core will then be holding approx. a gallon of water, so consider that when adding coolant to get the proper mix.
FWIW I've had great luck with the newer Honda 'Blue' coolant.

 

If you really want, you only have to drain some, to get the level down to the thermostat. Or just let it pour out while you quickly swap thermostats.

But it's MUCH better if you drain & rinse the system thoroughly. Can't hurt for it to be all clean.