Remove the coolant valve on the engine left side.
Inspect the coolant valve [A] at room temperature.
★ It the valve is closed, replace the valve with a new one.
To check valve opening just blow through the valve.
Valve Closing Temperature (for reference)
Standard: 70°C (158 F) or more at 25 kPa (0.25 kg/cm², 3.6 psi)