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Q: Car overheats, heater malfunction

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Several days ago, the car started overheating. Since then, it has been happening after quite short driving distances. I've noticed that the heater is malfunctioning then as well. It also happened that I drive around town and the operating temperature is as it should be. However, when I go on the highway, the temperature would start increasing and the heater would work fine. After having the codes read, one appeared indicating a bad coolant temperature sensor. I had the coolant flushed the other day, and it seemed to me that the overheating was even worse while I was driving the car afterwards. It was as if I was driving a car with a manual and the braking was like when you still have the clutch engaged and you let go off the accelerator. What could be causing the overheating? Could this be because I haven't still replaced the ATF?

A: I'm not real clear yet on what is going...

I'm not real clear yet on what is going on with your Mazda. Let's start with the diagnosdtic trouble code (DTC) that indicated a faulty Engine Coolant Temperature sensor. That needs to be replaced. Next thing: you may want to return to the service center that performed the coolant replacement to let them know that all is not well with the work they performed. Cooling system diagnosis includes things like: pressure checks and inspection for leaks, fan operation, test or replace radiator cap, verify ACTUAL coolant temperatures and compare to what the gauge on the instrumnent cluster reads. Verify that the thermostat is opening and closing normally. Be sure there is no trapped air in cooling system due too improper filling procedure. Do not let it overheat or engine damage can result! If you would like assistance on diagnosis of your overheating Mazda, an experienced YourMechanic technician can come out and take care of it at your home or workplace. Best of luck!

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