1999 Hyundai Excel Over Hearing

Hi I only just bought the car today, I live an hour away from where I purchased the car, I know the exhaust needs replacing and has only been taped but that's not the problem I had travelled 40 mins home when she decided to go from the temp being 1/4 to fully hot in a matter of seconds. I pulled over and called my daughter to bring some water, em when we did finally turn the car on to add water it didn't need any. There doesn't seem to be any oil in water or vice versa. Do you have any idea of what the problem is?