I have to replace the thermostat on my 99 f-150 4.6L V-8. No big deal for me but I don't want to drain any more coolant than I need to. Any idea how much I need to drain to get the level low enough to replace the thermostat? I'm guessing about 2 gallons might do it. Also - are there any tricks to refilling the cooling system or do you just fill from the expansion tank?

Thanks!!

 

drain three - four gallons should be it no rad cap put it in the expansion tank it will return it to the rad run the engine till temp top it off that it

 

Just remove the thermostat without draining any.. yeah it'll spill over the engine but it's nothing a garden hose won't fix.

 

^^^ I'm with you. I wouldn't bother draining any.
Pull off the hose and lift it high enough so none comes out.Take out the thermostat and replace. If your careful you might loose a quart at the most.