My coolant is boiling. I've replaced the thermostat, reservoir cap, temperature sensor and sending unit. No milky oil, no loss of coolant.

 

Welcome to the forum. You'll get more exposure to Sebring owners if you post your question in the Sebring section where they hang out. This is where you want to introduce yourself.
There are numerous threads there about overheating that might answer your question. If you still want to post the question, choose a title for your thread that describes your problem so that people can find it to help with their own problem.

You might have air trapped in the system. It will take several warm-up and cool-down cycles to work its way out. DO NOT use the bleed screw to bleed the air out. In an older vehicle, that screw will have seized and turning it will strip out its connection to the plastic housing, resulting inevitably in a leak. There are numerous possible causes for boiling over, the worst and most expensive but least likely is a blown head gasket. Rule out all the other possibilities before you plunge big money into it. Cheapest thing first.