Car gets hot?

Hello,

It sounds like you might have a faulty thermostat. Typically reliving the pressure will lower the temperature of a system. That's why you are seeing temperature going down.
If the thermostat fails then he coolant twill not flow properly through the engine and will make it over heat.
The thermostat can be changed out using simple hand tools.
Be sure to work on the vehicle when the engine is cold.

https://www.2carpros.com/articles/symptoms-of-an-overheating-engine

https://www.2carpros.com/articles/how-an-engine-thermostat-works
https://www.2carpros.com/articles/replace-thermostat

I have attached diagrams for your reference.

Please let me know of any questions.

Thank you.