Awwww
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it won’t explode, don’t worry. It may damage the car tho

Is something wrong with the coolant?

The car is probably low on coolant, which usually indicates a leak, have him top it up, and see if it fixes it, if it comes back, there's definitely a leak, then he ought to find it, could be as easy as a hose that's cracked, a loose hose clamp, or it could be the radiator, if it is, it can get pricey, another way to fix this is to take the car to a repair shop, and have them figure it out.
He should do some searches on repair shops to find one that's not too expensive, and can be trusted.
And no, the car won't explode, an overheating engine will usually just stall, and start agian when it cools down

Also, any wet spots under the car will confirm a leak, a properly working, healthy vehicle shouldn't have any wet spots under it

Dad is very happy with the advice, thank you for helping :)

Happy to help