Thermostat Stuck Open vs. Stuck Closed: Symptoms and Risks Category Bad Thermostat Symptoms A thermostat stuck open keeps an engine too cool; a thermostat stuck closed can make it overheat within minutes. A low temperature gauge and weak cabin heat point toward an open valve. A fast-rising gauge, steam, or boiling coolant calls... By Car Thermostats, 7 September, 2026
