Engine temp problems

Engine runs cool when the heat is on

Hey Scotty, ive been a fan for 2 years now after bought my first truck It a 2006 Chevy Silverado

Im having trouble finding out what’s wrong with my cooling system

i hadent checked the anti freez in a since last winter, this winter my truck over heated and I noticed I was low on coolant. After topping up I was leaking slowly and I think the leak is coming from the over flow but I’m not sure if it’s cus I may of added to much antifreez. The engine near get to 100 (normal operating temp) but when I turn the heat on the engine temp gadge reads 83 and stays there till I turn the heat off. Before this started the engine would heat up from cold and once it was a hot engine turning the heat on or off wouldn’t affect the engine Temperature. I don’t have a rad cap since I have the V6 engine I just have the over flow. Please help. Thanks you for all your helpful video.

I would change the thermostat and flush out the coolant and put new coolant in and a new radiator cap. If that didn't fix it, do this video https://www.youtube.com/watch?v=evpaTW2WJ5Y