问题:温度上升

Once i had to drive 20-25 min with no water in cooling system till i reached my mechanic.the engine cooled off we fixed the problem(leaking).and for few months the car was running as nothing happened.And every weekend i drive up hill to my home and nothing changed the car is a real beast but few days ago while driving up hill the temperature increased slightly then cooled off to normal and never heated back even though i was still driving up.could this be because of a thermostat problem or my engine is ruined.my car in regular driving in the city never warms up

我的车有15万里
我的车自动传输