Thats avery easy problem to diagnose. I would change mechanics. You simply let the car idle in your driveway watching the temperature. When it gets up too high check and see if your fans are comming on. If they are not comming on find out why. bad fan motors, bad relay?, loose connections. The fans are your problem.
One more question, I have seen many times folks complain there car is overheating when it is not. Some cars have a slightlyhigher spread from when the thermostat opens to when the fan comes on so the gage might go up a bit more at idle than it does going down the road. So how hot is it getting? Does it level out at some point or just continue to climb?
It’s certainly possible that the fan(s) not coming on is due to faulty fan system components, but that’s not necessarily the case. Sometimes the fans won’t come on because hot-enough coolant doesn’t get to the relevant sensor. A faulty thermostat or being low on coolant can be the cause.
I agree with you Gary for the most part. Low coolant especially. But he did say it operated fine at highway speeds or when the car was moving. A thermostat will cause it to over heat no matter what the car is doing . One simple visual test of a thermostat if the car has a temp gage is to simply sit in the drivers seat and watch the gages while it idles. Once the temp starts moving it will climb steady until the thermostat opens. Once this happens it will slightly drop or at least stop mving for a second and continue like this for a few minutes until it heats up the radiator coolant where it will then pretty much level out. I have seen cars where the thermostat opened at 195 and the fans kicked on at 212. This will show up at stop signs by your gage climbing a bit higher than where it normally rides when you are going down the road. I think about a 10 degree spread is more typical.
As usual GaryT gives the best advice for the easiest diagnosis/fix. You may just have an air bubble in your radiator which gives the same symptoms that you describe. While cold, open your radiator cap and pour in some 50/50 antifreeze/distilled water mix. If it take more than a little bit, then there may be a leak somewhere (mine was a bad thermostat gasket). The rest of the posts give some good ideas of where to check for the leak.
Second would be the fan but make sure to have a second person to watch the temp gauge and turn off the car when the temperature starts to spike. This can be done while making sure you’ve burped your radiator*.
*That what my BIL always called getting the air bubbles out.
Yes. I wasn’t talking about the OP’s situation from 18 months ago, but a general scenario where the fans don’t operate. Sorry I didn’t make that clear.
I had a similar problem that defied solution for several years, despite being looked at by several mechanics in different cities. Finally, my latest mechanic found it.
It was a physically mangled and somewhat melted connector in the wiring between the fan switch (or thermostat or something) and the fan itself. It looked fine on the outside, but if you disconnected the two sides there are looked inside the damage was visible. How it got mangled is unknown.
They fixed that and my car never overheated again.
I know its a bit late, but in future for anyone else
If you think that the water isn’t boiling, then maybe its the temperature gauge that is not working properly ??? that is, its only boiling when steam is coming out of the radiator !.
If the water is boiling, then the fans should be running ? were they ? If its boiling when the fans are working, then there must be thermostat problems.
Well , blocked radiators and failed water pumps are easily tested for . There is no way that they can be working “sometimes”…
Perhaps they tested the thermostat it it worked alright, so they put it back in ? But its the thermostat that can get stuck sometimes.!
The electrics can be intermittent too… maybe the fans only come on at really high temperatures…
I started noticing this on my 2009 Edge a few weeks ago. And almost always on a Sunday afternoon. Here’s the itinerary:
0930 Drive 12 miles to church (surface streets only)
1000 - 1130 Church service
1130 - 1200 drive to Costco (surface streets OR freeway; depending on the store we go to)
1200 - 1330 grocery shopping
Only surface streets are taken on the way home from Costco, but we usually stop at a fast food place to pick up lunch. And I wait in the drive-through. After I leave the drive-through, the air conditioner stops blowing cold air, and the temperature gauge starts approaching the red line. At this point, I turn off the AC, open the windows, crank the heater, and drive for about half a mile or so down the road. This action, without fail, brings the temperature gauge back into the normal zone, permitting me to restore the AC and close the windows.
I have looked into the engine compartment when not overly hot, and found the fan spinning. I have not yet pulled over during an overheat episode to make the same check.