02 cavalier coolant leak expansion tank

I have a 02 cavalier 2.2 it just started leAking coolant when in a drive thru. Steam started coming up from hood. When I looked under the hood the expansion tank was hissing and it looked like the antifreeze was coming out of the overflow tube at the top of the tank. What should I do? It is sitting still at the parking lot

Need to verify cooling fan operation and make sure the cap is good. If those things check out you could have a stuck thermostat, bad water pump or possible headgasket problem.

1) Turn the heater on high max with engine idle.

Are you getting any heat?

If yes, monitor temp gauge till temp go's down.
If No, turn engine off & let it cool down.

If no heat, there's a shortage of coolant because of a boil over or leakage
in the coolant system.

What caused the boil over?
bad coolant fans, fan relay/fuse, thermostat, plugged radiator core, or leakage in the coolant system.

Note - If your able to turn the HVAC on high max cool, both coolant fans should turn on.

ok, I had the car checked out by a mechanic and they could not find any problems with it. I took it home and let it cool down. This morning I filled it up with coolant, warmed it up and drove around a while. Nothing happened, all the coolant is still in it and no hissing sounds around the expansion tank. The cooling fan works fine. Before the engine would always go 2 lines over 195, the fan would kick on and bring the temp back down to 195. From my test drive and letting it idle for a while I couldn't get it to go over 195. The heat works great and the fan kicked right on when I turned it on and kept the temp down. I did notice that when I parked it the A/C line was sweating a lot and dripped a lot, but I didn't run the a/c at all. The thermostat was changed about 2 months ago and the car was driven from MI to FL. Any ideas what is going on?