My 03 Century is overheating changed the thermostat still overheating an no heat but if I take cap off the overflow canister an drive the car won't overheat gauge goes down to normal

Recommend combustion leak test. .. This will require a visit to local auto repair facility. ▪️https://repairpal.com/repair-shops▪️

got air in the cooling system,maybe? there is a bleeder screw on the housing to bleed the air out?

Hello, The leak is not an issue at low pressure, but the cap on the reservoir is causing the pressure in the engine coolant to rise (as it should). Removing the cap lowers pressure, so the leak is contained. First, Combustion gas test, then UV dye and pressure test for leaks with the engine cold, clean and dry.

I had this problem for a month now