I have a 10 ford explorer with 150k miles. It still blows freezing cold air but when I switch it to heat it only blows hot air when the car is moving but cool air when idle. Also it randomly the temp Guage goes up to hot for a second or two then goes back to operating Temps. Any ideas? I already replaced the thermostat.
Check your coolant level inside the radiator and top it off. You either have a leak or didn't fully bleed the system when you did the thermostat and the coolant is low.
Rent a pressure tester for the cooling system and pressurize it to 16 PSI. It should hold the pressure for a good while. If not, you're leaking coolant somewhere.
I did a flush and yes alot of air came out the system, thanks
Properly bleed the air out of the system. Sounds like air is trapped in the heater core.
I did a flush and yes alot of air came out the system, thanks
That's fine but did you bleed the air out after putting in the new coolant and how did you do it??
I emptied out the radiator, and reservoir and put in distilled water and ran the engine to push out any old remaining coolant and then flushed it again to make sure no old coolant was there, then I lifted the front end a Lil bit so the new coolant can pust out as much air out of the system as possible then, ran the car and let it get to temperature and watch the radiator with the lid opened to fill in more fluid as it needed until full then top off the reservoir and done.
Did you make sure to turn your heater on high to purge the air from the heater core as well?
Yes I did. A massive air bubble came out lol