Hello, I'm working on a 1988 Silverado. Here are the symptoms. I have to add anti freeze 2x week. Maybe more in the summer. It smells like antifreeze when the truck is running and water drips from the exhaust pipe, even after the truck has been running for awhile. The heater core is dry and not leaking inside the bottom of the plastic housing. and also you can hear gurgling inside the heater. There are no visible leaks that I can see on the outside the engine or on the pavement. The oil is clean and has no signs that antifreeze has been mixing with it. I'm starting to tear down the engine now. My question is, "Is it a manifold gasket failure, or do I need to go deeper and replace the head gasket?"