What in the world could be wrong with my husband's car?

we can't get his car to the shop until tomorrow but last night he ran to the store (about 5 minutes away) and then on the way home it got really really hot. He pulled over and had his dad bring him some coolant but it wasn't low on it. They cranked it up and it made it the rest of the way home. With it getting hot in only a couple of minutes, his dad thinks maybe the pump didn't work for some reason, but the belts are all just fine. He drives a Lincon LS v8. We are just baffled because we've never had any problems out of it before and not having any problems out of it now.. do you think maybe the pump just slipped or something? I now that it's hard to dingoes a car problem over the internet.. I'm just so curious as to what may be wrong and the price of getting it fixed may be. Thanks for your answers and guesses lol