Overheat at higher speed
 

Have 2008 Mazda3 Touring (hatch) with 52000 miles. Just noticed when I'm at higher speeds, 5th gear, the temp guage goes up almost 3/4 of the dial. Then as soon as I am off the highway it goes right back to the halfway point. Anyone ever experience this? I've always thought cars mostly overheat when idling and cool when cruising. Car has always been dealer maintained and never any problems other than normal service schedule. I'm considering if I should find a local maintenance shop or continue with dealer.

Any help?
 

OK - checked fluid level and it looks like it is at the max level (really hard to see even with a bright light!) Should I be concerned about driving it on the highway to dealer? Looks like I have some warrant left to 60,000 that would cover things like thermostat. Is there anything else I should check like clogged vents somewhere that would cause temp guage to go up while driving highway speed???

Your coolant temp gage is in the back of the motor, it wouldent be clogged or anything it's a censor. You should check the electrical connections to it to make sure you're not getting a mis-reading. when you are looking at your engine it is in the back right of it. You should see a little coolant hose that goes to the back of the motor, look right below it and you will see the little grey plug going into the block, check the wires on it, and you can even un clip it to see if the connectors are good. I woulden't risk driving it hot, even the slightest elevation of your tempature gauge can cause severe problems.

Does your fan stay on after you turn the car off?

It sounds like a thermostat problem though, easy fix! If you have insurance your insurance company should tow you for free at least 18 miles, I woulden't drive it there because any further damage could void what warranty you have left!

Thanks Shav - I did get it to the dealer and they replaced thermostat (totally under warranty) and no problem now. I did drive to the dealer - although I was prepared to stop and call AAA. But I found that the temp stayed right at a good temp if I had the heat on in the car.