I have a 1994 Toyota Camry that started overheating about a week after I bought it. It only does this at idle speeds. I had a pressure system check done, a new thermostat put in, and a new cooling fan installed. It stopped overheating for a couple of weeks, but then started doing it again.
I saw your answer to someone below after searching for a good block sealer: “If they DO suspect a blown head gasket or cracked block you might want to try a can of KW Engine Block Seal additive you can buy at your local auto supply. Drain out the coolant, add the can of additive to your radiator and drive the car for about 500 miles, then drain out the water/additive and install the proper mix of coolant and water to the radiator.