2006 Sebring Limited convertible, 2.7 V6, 85,000 miles, sealed coolant system (pressurized reservoir with two hoses)
Haven't driven it in the past year because: had to replace water pump (!$!$!), then replace and flush radiator, then replace battery, then replace starter, then finding/fixing an electrical issue with the ignition. I finally got the car running last week. NOW: occasionally (it hasn't happened every time), after some of the short drives I've taken, less than 10 miles, when I return home I discover that the coolant in the reservoir is boiling. The temperature gauge operates properly, rising to half way and staying there, never indicating overheating. I can hear the boiling when I get out of my car. (The radiator fans come on normally, which I've heard.)

What might this mean? What should I do?

 

Try replacing the radiator cap.

 

You have air in the top of that 3 hose black plastic "water jacket" or whatever u call it. When air gets trapped at top of it, it super heats and blows a hole in it. Checkout utube video for how to bleed air out of it. Its NOT that easy. There is only one video by an African American on utube that does it right. Look for it and u will be ok.

 

I do agree the first step is replacing the radiator cap. It may be more expensive, but I suggest going to a dealer for an OEM one to be the proper psi rating.

For bleeding, please check out this link

https://www.chryslerforum.com/forum/...-system-16293/

It outlines a fairly simple procedure to get most of the air out and then lets the normal heating and cooling of the engine to complete the bleed process. This process may require topping off the reservoir once or twice but is effective. The factory procedure is designed for the tech to fully bleed the system and not require the vehicle to return to the shop for topping off.

 

DON'T TOUCH THAT BLEEDER SCREW!!!!!!

Almost certainly on a car that old the screw will be seized into the metal socket. Turning the screw will strip the metal socket out of the plastic fitting that it is molded into. Then you will have a leak there and will have to replace the entire fitting.

If there's air in the system, it will work its own way out after a few warm-up/cool-down cycles. You might need to top up the coolant a couple of times.

When the fitting and the car were brand new and being filled up for the first time with coolant at the factory, that screw was very handy for bleeding air out of the system. That was then. Don't try to turn it now.

 

YES! THANK YOU. I replaced the cap, the boiling stopped. I've driven miles on it and it did not re-occur.