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Discussion Starter · #1 ·
Hi all,

Yesterday my engine overheated a bit. I was idling for about 15 minutes, waiting on something when the engine rpms dropped a little, like it was going to stall, but recovered immediately. It did not stall. I noticed the coolant temperature was way up. I immediately shut down the engine and checked on things. Coolant reservoir is full, oil level is good, no broken belt for the water pump or anything, no leaks of any kind. I suspect the fan isn't working anymore, looking back i'm fairly sure i didn't hear it kick on at all. Itst currently sitting at my mechanic shop for them to figure out. I waited untill the temperature was back in normal operating range, started right up, and drove to my mechanic with no issues, temperature stayed at normal temperature.

My main concern is, could this little overheating have led to damage to the engine? Head, headgasket, something else? The temperature at time of overheating was still under the high mark.

2008 Mazda 3, 2.0 engine, automatic transmission.

106034
 

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No Check Engine light? If you don't have a CEL or persistent issues, I wouldn't worry about it (because there's nothing to do unless you have signs or symptoms).
 

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Discussion Starter · #3 ·
No, no CEL. Double checked with my scanner, no codes. And it drove fine, drove it for an hour to my mechanic, as long as i was driving, temperature was normal. Let it idle for a little bit when i got there, idled normal. Temperature climed slowly while idling.

Just a thought i had, since engines generally don't like to run too hot.
 

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It could have damaged the head gasket, but probably not. If it is overheating at idle it is almost certainly a fan issue. The good news is if you did fry your engine, replacement motors for this car are cheap, and not the hardest thing in the world to swap out.
 

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Discussion Starter · #5 ·
So i got my car back yesterday, mechanic said he couldn't find anything, and it was all working fine. He had it idling for almost an hour on two occasions and didn't overheat.

I plug in my scanner, drive it up to temperature, and sure enough the temperature starts to climb again at idle. At some point, something started to make clicking noises, i couldn't really tell where it was coming from. A constant clickclickclickclick. Shut the engine off, temp was 101C. Started it again, and the clicking was gone, haven't heard it since. Ran it until 103C, never saw the fan come on.

Temperature when driving is between 88C and 92C, so that tells me the thermostat should be fine.

What can i check myself to verify the fan isn't working correctly? I don't have much electrical knowledge. Did find a 40 amp fuse that said fan in the engine bay, but not sure how to see if those big ones are busted. It's a big metal one with 2 wires bolted on each side, probably disconnect the battery before removing one like this?
 

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I have a similar issue with my speed3. If it happens when idling I usually just rev for a little bit until it drops back to normal. I had a throttle body replaced by a shop who put the stock tune back on my car, and it idles lower now so that's what I attribute the issue to.

I'm sure you haven't done any damage if the CEL didn't come on when it heated up, as it has happened to my car many times and have had no problems. I have been working up the courage to spend the money on an accessport so I can retune my ECU, so if I do, I'll let you know if raising the idle fixes my problem, but I suspect it will.

You said the idle dropped but didn't stall, is it still at that lower idle speed? How many RPM do you get when you idle? around 750 is where I heat up. Also, a coolant flush or oil change may help your situation, too.
 
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