Overheating in Cadillac Deville 2002 Car shows overheating. No signs of leakage

Hello, if there is no external leak found, it is a wonder where the coolant is going. I would strongly recommend to have a pressure test performed of your cooling system. Refill the system, purge air out of the system, then perform a pressure test. If you do not have the proper tool and you will need to go to a shop that does and have them do it. It will figure out what is going on with your car. Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops