2013 mustang gt 5.0 overheated…

The 2013 mustang 5.0 with 89k miles I just bought 3 weeks ago overheated at idle today. I had it parked in my driveway (running) after driving it for 20 minutes so it was already at operating temperature when I parked it. After I parked it I left it turned on/running while i went inside my house to grab something and when i came back there was a ton of smoke coming from under the hood and when I opened it the coolant in the reservoir was boiling over and the temperature gauge was all the way at H. After seeing this I immediately shut off the car and opened the hood again.

As far as I know the temperature gauge was in the middle before going in the house and when I came back probably 2-3 minutes or so had passed. So presumably that’s how long it ran all the way at H. It still had coolant in the reservoir when I came back outside but it was low towards the bottom of the reservoir but definitely not completely empty…

Also last night I had actually checked the coolant and it was full. So whatever part(s) failed literally just went bad while the car was parked in the driveway for a couple minutes.

How likely is it that I damaged something (heads, head gasket, block, etc.) from running it all the way at hot for 2-3 minutes idling only? What could the likely culprits be? The car has never overheated, smoked or anything like that in the 3 weeks I’ve owned it. I’ve checked the oil dipstick and the oil looks normal, no chocolate milk mix. About an hour later after it had overheated, I opened the reservoir and topped off the coolant and then started the car and drove it around the block for about 10 minutes. Everything seemed normal and temp gauge never went back up… Car started up fine and ran smooth in the short distance I drove it. Am I likely in the clear?

I wouldn’t worry about engine damage from idling hot. Is the radiator fan working?


Not sure but that would be a good place to start. Is the best way to test it is to just turn the car on and let it idle (while watching the temp gauge to make sure it doesn’t overheat) and just see if it comes on once the temp gauge reaches 1/2 way or soon after?

I had similar experience w/my Corolla a few years ago. Driving slow speed in stop and go San Francisco traffic jam, noticed a lot of fog ahead. Just figured fog normal thing for San Francisco. Then noticed fog only in front of car, no fog to rear or sides …lol… Stopped car, turned out radiator had split a small seam, steam pouring out top of radiator. Caused by radiator fan not turning on when it should, faulty coolant-temperature switch… Replaced radiator, didn’t cause any other problems, other than perhaps causing water pump to spring a leak later.

Engine compartment fan operation is first thing to check.


You may have found out why the previous owner sold the car.

Sorry to hear it. Good luck.


That would be seller’s loss if the car only needs a radiator fan motor.


When I went to buy the car I idled it for at least 20 minutes while talking with the seller, AFTER test driving it thoroughly and the temperature already at warm/operating. And the gauge was still in the middle. So I am 99.999% sure this problem developed after buying the car. Also it’s never overheated before since I’ve owned it and I’ve had it idling for much longer lengths of time than 2-3 minutes and it’s never overheated on a 4 hour road trip I took with it too.

Check the fan relay and the cooling fan itself. I think the fan kicks on at 209 F, or just past mid gauge. I’ll check my manual and report back.

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Even with the overheating problem that is a really bad practice . It only takes a minute for someone to jump in a drive away with your vehicle . It is also too much temptation for a young child who could possibly put in gear and damage car and hisself.

Our local news has at least one story a week of someone driving off with a left running vehicle.

Sure check fans but I’m not sure the fans not coming on would cause it to heat up that fast. A bad water pump could cause lack of circulation at low speed and of course a bubble from a head gasket. On a used car once I had a frozen blockage in the heater hose that caused an overheat in less than a mile. But that was after it sat out all day. So like on any used car of unknown maintenance, used the test kit to check for combustion gas, check the fan and I’d be replacing the hoses, thermostat, and water pump while I was at it. If it still over heats you are out a couple hundred dollars and it will still have to go to a shop. Wouldn’t hurt to check the radiator flow either. They are fairly cheap now if you are a diy er. After that, I dunno, internal blockage?

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Cooling fan electrical wiring…

The temperature sensor is the cylinder head temp sensor. That goes to the ECM/PCM which commands cooling fan Low or fan Hi depending on which relay gets powered. You can jumper the relay terminal 30 to 87 on each to see if both speeds run. If each run the fan is OK, one of the relays may be bad. Swap it out, they are cheap.

If you have an OBD2 scanner, check to see what the cylinder head temp (CHT) reads and if there are any error codes. If your gauge works, and you can read it on the scanner, the CHT is likely OK.

I went out to the car again this evening (hours after it first overheated) and topped off the coolant with the engine completely cold. Then I started it. I waited a long time while looking under the hood to see if the fan would turn on while my room mate sat in the drivers seat to be ready to shut the car off in case it started overheating.

We waited for almost 25 minutes from the cold start and the fan never turned on…however the car temp gauge stayed right in the middle and it never overheated. Up until about the 30 minute mark, the temp gauge finally started creeping up and my room mate turned the engine off. We didn’t let it get to H only like 2/3 up. The coolant in the coolant reservoir had not gone down at all after running for 30 minutes so is it correct to say that nothings leaking and the culprit is definitely the fan? Both radiator hoses got hot so I’m not sure if that eliminates anything.

Also we shut the car off once it started overheating and then immediately restarted the engine and the temperature gauge was now reading all the way down at cold which makes no sense because the the gauge had shown it was overheating just a few seconds ago. It took roughly 25-30 seconds before the gauge finally started moving from cold but when it did start moving it went back to showing 2/3 to H at which point we shut the car off again. What does this point to? Something is definitely wrong with the gauge since it takes 30 seconds to display the correct temperature, (which may or may not be a separate issue) but based on the fact that earlier in the day the coolant boiled over and out of the reservoir means that the car is indeed actually overheating in addition to the gauge also possibly being faulty. Any advice is appreciated!

With the ignition off, using a pencil or some type of probe try to rotate the fan blade, if the motor has seized it will be obvious.

Check the fuses in the diagram shown above. Using a test light or voltmeter check for power and ground at the radiator fan connector.

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Yep I used a pencil to see if the fan was physically stuck or something but it was able to rotate freely without any obvious blockage. So the next step would be to check the fuses and then the fan relay for power. Does the fact that the fan never came on and no coolant was lost after running/idling for 30 minutes pretty much 100% point to the problem being something to do with the fan?

One of the mechanics I’ve worked with before thinks the thermostat and coolant temp sensor would be things to try before the fan in terms of the overheating and the gauge taking a long time to read correctly. Does this sound accurate? Common sense tells me that if the fan didn’t kick on after 30 minutes then that’s the issue but On the contrary the engine overheated after just 2-3 minutes of idling this morning while this time it idled for nearly 30 minutes before beginning to overheat. Doesn’t make sense…

Test these things in whatever order you want, I would start with the fan motor, these wear out. It only takes 5 minutes to test a fan motor for power, you waited 30 minutes for the engine to warm, I would have driven the car for 3 miles.

I’m going to shut up shortly but if the thermostat was a little lazy and opened up to let cooler fluid in, that could explain why the temp gauge read lower again. Of course if there was a combustion bubble blocking the flow, that could explain it too. I’d want to get that test kit and rule out a head gasket.

You’re right, I started the car and let it idle for 10 minutes at which point the car was at operating temperature. So it basically idled at operating temperature for 20 minutes before it began to overheat

It takes a long time for the engine temperature to climb with the hood up. Much heat is lost through the radiator even with the fan off, if there is a gentle breeze the fan may never be needed. When you arrived home before the overheating, the engine was 200 degrees or higher, the fan will be needed in a short time.


This engine does not have a coolant temp sensor or temp switch. It only has a cylinder head temp sensor… from that the engine computer calculates the what is sent to the gauge. That is the 30 second delay.

Jump the relays and test the fan for low and high speed. It is a 5 minute test. If the fan runs on both speeds, change the relays.


So you’re saying the 30 second delay is normal and nothings wrong with the gauge then?