Ok. So my car has had fairly steady running temps of 180-195F in wonderfully hot Texas. Upon shutoff, air from the radiator cap neck (ast elimination back in the day) naturally escapes into the overflow tank. When I say air I mean it sounds like boiling water, but I can clamp the line and it stops, so yes I know it is just air dumping in the overflow. But my problem is that it is So forceful that it is causing coolant to spill out from the little vent hole and also from where the overflow tube goes in. Any help?

 

Replace the AST cap. Thats what did it for me. I had the same problem a few weeks ago. I went ahead and rplaced the AST and radiator cap.

 

i concur, my 7 made the loud gurgle noise, i bought a greddy cap for the radiator and used that cap for the ast and it stopped, i guess the ast cap was bad and leaking a tiny amount of air.

just a little longer till i have my aluminum ast.

Thomas

 

It is boiling when you shut it off. You have a "largish" air bubble in the system - at the filler neck probably. This air bubble lets the pressure in the system fall when you shut it off because air is compressable and that lets it boil a little. The bubble is there because the cap probably is getting old and lets air in under -vaccum-, when the engine is cooling off. This defeats the coolant "suckback" that would normally keep the system full of coolant. Replace the cap. Then the system will suck back the coolant from the overflow tank, there will be only a very small bubble of air in the filler neck, and the pressure will be high enough that it will not boil when you shut it off.

 

The AST has been eliminated, using the '86 cap neck. And it's not "boiling." It is just air from the system escaping into the overflow. I'll try replacing the radiator cap and see what happens. Thanks for the help so far.

 

I you have air escaping every time you shut the car off...

Here are the 2 most probable causes:
1) Air being drawn back instead of coolant due to bad pressure relief cap peripheral seal, or a leak in the tubing between the filler-neck nipple and the overflow tank (you said "air" was escaping at the overflow-tank nipple).
2) Air being pumped into the system through bad o-rings.

 

ha it was the cap. always overlooking the little things.