Select the maximum heater temperature and blower motor speed settings. Position the control to discharge air from the A/C vents in the instrument panel.
WARNING: Do not stand in line with or near the engine cooling fan blade when revving the engine. Start the engine and allow it to idle. While the engine is idling, feel for hot air from the A/C vents.
CAUTION: If the air discharge remains cool and the engine coolant temperature gauge does not move, the engine coolant level is low in the engine and must be filled. Stop the engine, allow it to cool and fill the cooling system. Start the engine and allow it to idle until the normal operating temperature is reached. Hot air should discharge from the A/C vents. The engine coolant temperature gauge should maintain a stabilized reading in the middle of the NORMAL range, and the upper radiator hose should feel hot to the touch.
Shut the engine off and allow it to cool.
Check the engine for coolant leaks.
Check the engine coolant level in the degas bottle and fill it as necessary."""
The coolant level in the overflow went down overnight last night. It's still above where it should be though in the overflow reservoir.
I just tried running it like that said and the temperature gauge never moved. When I started revving the engine and held it at a steady 2k RPM, then the gauge went to where it should be. When I let go and let it go back down to idle, it dropped to cold again.
Where is the head gasket located at in the engine? Is it above the spark plugs, which are above the exhaust manifold? I don't see any weird smoke coming from the exhaust.
Coolant reservoir hasn't sucked in what it should because of the air in the system.
Doesn't work that way as air compresses and water/coolant doesn't therefore it will overflow when hot. The system blows out approximately a quart of coolant when system is fully hot due to normal cooling system expansion and then returns the overflow coolant when the engine is shut off/cooled down if the radiator cap is working and is the right type. No lever release radiator caps should ever be used on systems with overflow tanks. If in doubt, replace the radiator cap with an OEM design.
I'm probably over-reacting, but what signs should I be looking for if I damaged my head gasket?
Depends on if you had a major overheat occur. Usually the oil will end up with coolant mixed into it so the oil now looks like chocolate milkshake. You will normally see constant white steam out the tailpipe when cold and it does not stop when fully warmed up like condensation in the exhaust does as the exhaust system gets up to operating temps. Sometime you can see external leaks where the head gasket is located between the head and block and other times it is internally leaking into the cooling system so exhaust gases can be bubbling in the radiator neck or pressure tank when the cap is removed.