Hello Everyone,
I was contemplating replacing the thermostat myself on my 2010 Ford F150 5.4 V8. Seems fairly straightforward. The tutorials that I found start with draining the coolant/fluid. Can I remove the thermostat housing and replace the thermostat without draining the coolant? Is there alot of coolant in the top hose that will leak out when I remove the thermostat housing? I didn't know if the tutorials mentioned this because they assumed a coolant change was also going to occur or to prevent major coolant leakage when the housing is removed. Thanks in advance.

 

Just drain it down to below the level of the thermostat housing. Change thermostat, and put the coolant back in.

But since you're there, why not replace the coolant with fresh clean stuff? Can't hurt.