if the remaining coolant is still visible in the expansion tank then just top it up with a premix of anti-freeze. If you haven't got any anti-freeze solution top it up with water (when the engine is cold). Apart from making the engine bay wet and maybe scalding yourself there shouldn't be any damage.
The system is pressurised in order to make the boiling point of the coolant higher.
The system is pressurised in order to make the boiling point of the coolant higher.
