FWIW, I remove my thermostat for a good flow when I flush out my cooling system. Removing the T-stat will flow more water than a fully open T-stat. This gives a good flush that removes more contaminants regardless of water temps. It's not hard to remove.

Distilled water is a must for cooling system refill and only costs around a buck a gallon. I buy 4 gallons at a time for the truck.

Place climate controller on heater setting,
drain cooling system,
remove T-stat,
leave pet**** open & flush with garden hose while engine runs (Goosing the trottle ocasionally) 'till water runs clear,
stop engine & let drain,
close pet**** & fill with distilled water then run engine for a few minutes,
drain again through pet**** and repeat previous directions,
after second flush with distilled water drain system and replace T-stat (with new if desired),
close pet**** and add required amount of antifreeze to obtain a 50/50 mix based on cooling system capacity,
start engine and let warm to operating temperature,
top off with distilled water to proper level.

It seems complicated and drawn out when its in writing but it goes quickly because with the T-stat removed you wont need to wait for a warmup at every flush & drain interval.

Good luck.

 

I'm planning on doing this with my regularly scheduled oil change next month...97 F150 4x4 4.6 automatic...is there a radiator cap under the plastic fan shroud housing? Or do you just fill up the system entirely from the coolant resovoir? Maybe it is a dumb question, I have yet to remove the shroud and and can't see a traditional cap anywhere else. Thanks.

 

AWH - there is no longer a radiator cap on newer systems anymore. They now use what is called a 'degas' bottle that collects the overflow from the radiator. Heard it called a radiator, overflow, and coolant jug. You fill the radiator through this bottle and cap. The cap is under pressure like the old caps were so be careful. There should be a cold fill line marked on the bottle. Good luck.