Cooling system "rumbles" for several minutes after shut down, even with "cool down" before shut down. Is this normal? Temp stays just below 1/2, no indication of leaks, radiator is relatively new.
94 touring, 79k on car, 18k on Mazda installed engine. Do I need to be looking for something amiss before it becomes big trouble??

 

Yes that is common. It is air pressure releasing which causes a coolant gurgling sound. If you eliminate your AST it goes away.