I have a 73 SD 455 pontiac engine that when at idle I don't see coolant flowing at the top of the radiator. The heater blows hot air but, there's not pressure on either top or bottom hose. What could cause this to happen?

Before noticing this I drove the car for about 8 miles on the hiway and has I exit the car shutdown. The next day the car started right up. I did not see any external leaks but I could hear on one side of the engine little bit of a sizzle as though there was trinkle of… Continue