Question about car engine?

check for t/stat being stuck open/have a competent garage look it over/

Sounds like your thermostat is stuck open allowing the coolant to flow through the engine without getting warm, you need to get the coolant system flushed as well. Most thermostats restrict the flow of the coolant until the thermostat reaches 195degrees. I don't think this points at the water pump or the serpentine belt or the engine should overheat and that will turn on the check engine light and give you toooo much heat

This problem you described could very likely arise from a disfunctional thermostat or water pump. The thermostat is what tells the coolant to start flowing from the radiator to the engine, and back, when the engine starts to get a little hot in order to keep operating temperature. The water pump, however, is what pumps the coolant from the radiator to the engine, and back.

Have a technician take a look at it to find out which one it could be.

Would you know a stupid answer if I gave one? Try adding coolant and purging the air trapped in the system genius.