Re: Cooling situation, looking for advice
A leak can be either way - water getting into the chamber under vacuum or just sitting, or combustion gasses getting into the cooling system. They don't always leak both ways.
Pressure checking often nails it, but there's another way too.
Radiator shops and decent repair shops have a chemical tester - made by Stant.
It sucks the air out of the radiator through a blue liquid chemical. If the chemical turns less blue, clear, or pink, it means combustion gasses are in the cooling system - a leak.
Combustion gasses collect in bubbles - bubbles don't cool, thus causing overheating and fluid loss when the bubbles expand.
Gaskets seal 4 things, combustion, water, oil pressure passages, crankcase. Leaks can occur in any combination and or in any direction.
A small leak in the radiator or hose can pull in air, the air collects, expands, and causes overheating too.
Air, being thinner, can get through where water won't. Sometimes a gasket forms a flap, only opening one way too.