I am going to flush and refill my Ranger cooling system. Yesterday I noticed that the temp gauge was sitting almost on HOT. I checked the sensor and it is good. The gauge is also working properly. I checked the fan clutch and it is OK. When I opened the radiator cap it was caked with gunk. I am thinking the thermostat is probably caked and or stuck closed. Should I remove the thermostat before flushing or see if the flush makes it open up? I will be replacing it with a new one.

 

If your going to do it, do it right and remove/replace the thermostat. If you only drain and flush without removing the thermostat, and it is gunked up, you'll have to re-do the whole process over again.
If your flush dosen't remove/clean the thermostat you'll have to drain again and then remove it.
Why take a chance on trying to save a few bucks.
Grumpaw

 

Grumpaw---Thanks for the input and advice. I will just do that. I just got back home with the new thermostat. I will replace it then put in the flush and go from there.

 

Also swap around the heater hoses at the firewall, so you reverse flow thru the core, if radiator was "gunky" then core will be as well
You should reverse heater hoses every year or two to help core to last longer, on ANY vehicle