I borrowed a vehicle and the engine got damaged?

Hi guys… I m in a bit of a jam and i would like to know your opinion. I recently borrowed my wife s, uncle s van to conduct some business. The van is a late model ford ranger. He had the van over ten years now and it us used for work in his business. The vehicle isn t in mint condition or anywhere close.it just there, but not falling apart either. I borrowed the vehicle and upon starting noticed that both the gas and temperature gauge was not working. The owner gave me the van and I went about my business after about 1 hr of driving the van overheated and shut down. There was no warning signs or smoke until the vehicle had cut off. It won t start and has been two days. I haven t told the owner what has happened because afraisd I will have to buy back an engine now… But in my defense I could not have known that the vehicle was overheating because the temp gauge was not working… Go ahead tell me your opinion and what I should do please because I m totally confused.

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