I need to change my thermostat in my 1992 F150 5.8L V8. Do i need to drain the coolant? Completely? Just to a certain level? Not at all?

thanks,

Imsorope

 

Dont have to. You're gonna spill some even if you do drain it.

 

I usually open the petcock on the radiator and drain some out,you'll probably spill some unless the thermostat is stuck open

 

Well, think about it. You need to drain it to a level lower than the thermostat housing.

 

Yea I drain it down a ways, Anti freeze is kinda pricey and I don't want it on the ground.
The water I drink and bath in comes from under the yard!

I drain it to a clean bucket and keep it clean, when done with repairs I filter it through a couple of clean rags and putting it back in the radiator where it came from.

As long as coolant tests "good" is clean and "green" I do not replace it.

 

Definitely helps to drain it. I recently replaced mine (different engine though), and it is helpful to drain it. You'll still spill a little, but less than if not draining it at all.

And of course, don't forget to bleed the system once complete.

 

Exactly as danr1 mentioned.

Coolant is pricey and I grab several jugs whenever I find it on sale.

And I also use clean rags to strain the recovered amount too.

 

I've always used a coffee filter. They fit perfectly into my funnel.