Why does my truck overheat? I changed the thermostat thinking that would solve the problem. It never overheated before. Now it overheats no matter what I do. When I turn on the heat it overheats faster. What do I need to do??

You may need to replace the radiator, due to phosphate scale blocking the passages:

https://www.askmehelpdesk.com/cars-t...tml#post235973

You may have to replace the water pump and test to see if your radiator still holds good pressure. Also try bleeding out the air pocket in your block. Some cars/truck have bleeder screw located near the thermostat.

I meant "radiator cap" still holds pressure.