With your coolant reservoir empty, your coolant system can’t draw in extra coolant when it needs it. This can lead to overheating. You can top up the reservoir, but you also need to identify where that coolant went. These are the most common sources of coolant leaks:
There’s a leak in the radiator, heater core or one of the hoses.
The radiator cap is stuck open. Hot coolant leaving the system evaporates quickly.
The water pump or water pump seal is leaking.
The engine has a blown head gasket. This lets coolant enter the combustion chamber and go out of the exhaust.
