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I'm having some concerns with my car's engine temperature. Last weekend after being stopped at an intersection, the engine temperature went up higher than usual, about 75% of the way to the red line. I believe the AC was on. Once we started moving though, it came back down to normal (just under 50%, maybe 45% or so) and it was fine the rest of the night, even when stopped. It was in the high 70s.

The car has been fine during my relatively short commute all week, about mid 50s outside temp in the morning and high 70s in the evening rush. I had the car in to put the summer tires on and asked them to check the radiator fluid, and they said it seemed fine.

Today the same thing happened on the way to the mall, only a bit further than my work is from my home. And on the way home, the temp was fine until we had some stop and go lights in a 25 mph zone. Once we got moving again though it dropped to normal.

The radiator fan is operating, I've heard it come on while driving, and it's also been running after I shut the car off if needed. I've checked and haven't found any evidence of a leak, and since the service station didn't say they had to top off the fluid, I'm assuming it was fine (and I was told they didn't see anything unusual with the level).

There are no check engine or other warning lights on.

I bought the car new, and I don't ever remember seeing the temperature go above the half way, even running the AC in much hotter outside temperatures.

Any idea what this might be, and how the problem can be isolated?

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2 Answers

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You said that the service station didn't mention having to top up the coolant, but I'd start by checking the coolant level yourself. The coolant overflow bottle should be prominent in the engine compartment, and the min/max levels should be well marked.

If the coolant level is good, perhaps you have a failing thermostat. This could result in higher than normal operating temperatures.

Also, some vehicles have a two-speed radiator fan. While you state that you can hear the fan running, if it is a two speed fan, perhaps the high speed is not kicking in, and you're getting only low speed.

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Thanks, I'll check and report back. I don't recall hearing the fan speed vary, but I may just not have noticed. –  Andy May 7 '13 at 0:01
    
I have an obd2 reader, could that help me troubleshoot? –  Andy May 8 '13 at 1:32
    
Can't hurt, but I can't think of any super-likely codes for these conditions. –  mac May 8 '13 at 19:48
    
Turns out it was the coolant. Even though they checked several times, the last check they said was slightly low but shouldn't cause an issue. They added more anyway and its back to normal. –  Andy Jul 19 '13 at 22:29
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A fan problem or radiator problem seem likely. Clean out any debris near the radiator, and check the fins for build up of leaves/bugs etc. It could be a clogged radiator - test for cold spots or drain it.

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