just to reiterate, my car did this for 2 years with the low pressure cap on. Changed the cap - problem solved. Car also ran a bit cooler too. You should take it as proof though, that your car is getting very hot. I'd highly recommend a drop-in radiator. Best mod I ever did.

-pete

 

Replace the stock AST with a metal one like a Pettit, replace the thermo-housing coolant cap, burp the air out of the system, and top off coolant. Mine was noisey as hell(actually embarassing when you can hear it with hood closed in a parking lot and feel the thumping leaning on the fender). I thought I was about to blow a coolant hose until I did the above. Now it's quiet, and all I hear is cool-down "ticking" and a tiny flow noise when coolant runs back into the AST as pressure drops.

 

I think in general these cars start to boil at about 235 or 245 so if your runing hard you'll get there in a hurry when you shut the car off but if your just running for groceries and its doing this than hey somethings amiss.

 

with tight system and fans on full time, sys pressure has dropped to zip, though still hot. Then stop things and hot engine points get stagnant coolant boiling, pushing out coolant, gurgleing.

bacK fans off a minute before shutdown, raising system pressure to prevent any boiling aft shutdown,