All I have a 2008 PT Cruiser that is over heating.

Service the cooling system and make sure the cooling fans work. Flush, new coolant, hoses etc. Water Wetter in the coolant will help keep it running cooler.

Ok... so there are no coolant leaks visible. Assuming the water pump is doing it's job. You can hear bubbling fluid form under the hood when the vehicle is parked and idling. You say there is no visable coolant leaking. It's possible there may be air trapped in the engine's water jacket. If so, the engine would be operating at a slightly higher temperature. Check the operating temperature of the vehicle has a temperature gauge. If no temperature gauge, purchase or borrow a temperature gauge gun from a local auto parts store. Is there coolant passing through the radiator cap and going into the coolant recovery tank? Was the thermostat installed correctly, that is not installed backwards? That can happen. Most, if not all thermostats have one side stamped "this side facing engine" or something of that nature, either stamped or imprinted on it. I'd check that. It'll take a little of your time, and the cost of a new thermostat housing gasket & fresh coolant.

Copy, There are no visable leaks. If i drive long distance the engine will heat then as thermostat opens cool down to normal op temp. When I drive long distance it surpasses normal op temp and overheats in which I have to shut down and allow to cool. That is the only time I get boil over. I did install a new thermostat per temp recommendations for this motor.

Cooling fan is working.

If this is a high mileage engine you might be looking at a worn timing chain. A worn timing chain will cause the valve timing to be retarded (late). This will cause the engine to run hot and boil over when you shut it off. You could have a bad knock sensor. The knock sensor is like a microphone that listens for denotation. When denotation occurs the knock sensor sends a signal to the computer to retard the ignition timing until the denotation stops. Severely retarded ignition timing will cause the same symptoms as retarded valve timing. If you have a valve tap or other engine noise the knock sensor may be picking that up and sending a signal to the computer to retard the ignition timing. Hope that helps! Jim