Chevrolet Repair Questions? Ask a Mechanic for Answers ASAP
Hello and welcome.
Another possibility is a head gasket problem.
This engine in know for the rear headgasket to blow and cause overheating. A blown gasket can cause combustion gases to be forced into the cooling system causing air pockets. Air pockets will cause the roblems you are having.
Suggest a a cooling system pressure test.
Removing spark plugs and inspecting for signs of burning coolant would show this problem.
Ya, nobody likes to hear that, but it is quite probable.
need help on a 1999 Chevy K3500 pickup with a 7.4 L