What common issue could cause a high temperature in a coolant system?

A thermostat stuck closed is indeed a common issue that can lead to a high temperature in a coolant system. The thermostat acts as a regulator for the flow of coolant through the engine and radiator; it is responsible for ensuring that the engine reaches its optimal operating temperature. If the thermostat is stuck in the closed position, coolant cannot circulate through the engine to the radiator for cooling. This can lead to overheating because the heat generated by the engine cannot be dissipated effectively.

While other factors may affect the coolant system, a stuck thermostat has a direct impact on the flow of coolant, which is critical for temperature regulation in the engine. When the thermostat fails to open, the engine can quickly overheat, resulting in potential damage to engine components and overall system failure.