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Strange overheating symptoms

I’ve been having a very strange issue with my 2012 200. The cause of the overheat keeps on changing so I have no clue where to start and it’s been puzzling every mechanic I’ve talked to about it and had take a look. My issue began with a general idle temperature rise, but never overheating fully. Then about a week later it also happened when I drove on the highway above 55 mph. It has been going like that for a while now but today on a trip with my wife the temperature gauge spiked out of nowhere into a full overheat. Ended up pulling over and all of the auto repair shops are closed for today, so I don’t know what to do. Then as I was driving to a different repair shop (no more than 2 minutes away) suddenly the temperature gauge dropped to 0 and the battery light came on. I quickly pulled over and took a look under the hood. Coolant boiling, no leaks, nothing appearing to be wrong other than the coolant boiling. I’ve been puzzled by this over the last couple weeks and haven’t been able to pinpoint down to one issue, and I really need to get back on the road and am left with just being able to do repairs myself and my limited car knowledge. Any similar experiences or advice?

Are all the belts on ?

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Coolant temp and battery light point to belt as my first thought. New belt and check for things leaking onto the belt that might cause slipping. Was it raining?

Everything is dry, I live in Arizona so usually the only weather issue is heat. All belts are on though.

A belt can appear to be on its tracks, but still slipping. You could try spraying water on the belts one by one with a spray bottle, and see if you notice anything different happening with the water spray experiment. Given the nature of the symptoms I’d suggest rather than trying to debug it yourself, not start the engine any more & just have the car towed to the shop. Overheating incidents, even those lasting just a few minutes, can do very expensive to repair damage to the engine. If your shop can’t figure it out, take it to a dealership. If they can’t figure it out, ask them to let one of their techs drive the car to and from work for a few weeks. Eventually it will happen to the tech and then some clues will be discovered.