I have an 02 Sebring with the 2.7 liter motor. It has 100,000kms on it. I started having cooling problems with low heater heat and the rad boiling over in the plastic coolant tank. So I changed the thermostat which is located halfway down the block. I filled both the motor and rad with antifreeze to prevent vapour lock. When I started it the car ran fine with lots of heater heat no temp over heating and the top hose was hot and the bottom hose was warm. I took it on a road trip and it overheated and I had to pull off the road. The top hose was hot and the bottom hose was cold. Thinking that the new thermostat had not opened I let it cool off and then started it and ran it with the rad cap off to get rid of bubbles but it soom boiled over. The top hose was hot and the bottom hose was cold. It has a pressure bleed screw on top of the top rad hose housing which is broken as the bleeder just spins in the housing. So I tried running it several times with the rad cap off to get rid of bubbles until it soon boiled over. Both electric fans are working.Does any one have any suggestions thanks artie

 

Overheating can be cause by several things. You could have a plugged radiator due to internal problems. It could be covered with leaves and debris externally. Your thermostat could be bad or installed upside down. Your water pump could be bad. You could have a leak in a head gasket. Your pressure cap could be bad.

When you mention "The top hose was hot and the bottom hose was cold" are you referring to the heater hoses or the radiator hoses? Either way, it's a sign that the thing may be plugged internally, although if it's the radiator, you can't rule out the thermostat. A plugged heater core won't cause the engine to overheat, but if there's enough internal problems from corrosion, both the radiator and heater core could plug up. If you have maintained proper coolant, such a degree of internal corrosion is unlikely. I assume you replaced the original coolant with the same type. Replacing gold coolant with green is not a good idea.

The system, if working properly, should rid itself of air after a few warm-up and cool-down cycles without the necessity of fooling with the bleed screw. Too late now but I would recommend never touching that thing.