My Mazda 6 started overheating during a heavy traffic day. Ever since, I noticed it would only start over heating only when the car is idle at a light, traffic, or parked for about 5 minutes and then slowly start creeping up. If I give it some rpm, the gauge comes back to normal reading. *Additional info - Heater only works when riding - I have to add a bit of coolant everyday - Changed thermostat, fan control module and fans work well. My suspicion is the water pump has gone bad. Help!!
I'm too new to comment, what year is it? What you describe makes it sound like the water pump isn't getting the correct power from the belt. Check all your pulleys and the tensioner, if one thing isn't working right on that belt it will cause other things to go wrong down the road.
Also driving warm (hot) regularly can cause innocent leaks from hoses because they aren't meant to get too hot. Easy test, after driving, park and wait 20-30 minutes to cool off a bit and fill up the car with luke warm water. Lay cardboard under the engine and radiator. Let the car run for 2-3 minutes. You'll find dripping coolant if theres a leak.