When the thermostat (also known as the water temperature control valve) of an automobile is damaged, the following problems may be caused:

1. Engine overheating: The main function of thermostat is to control the temperature of coolant flowing to radiator, so as to keep the engine in a suitable working temperature range. If the thermostat is damaged, the coolant may not flow to the radiator normally, resulting in overheating of the engine and even engine damage.

2. Unstable engine temperature: The damaged thermostat may lead to unstable flow of coolant, which makes the engine temperature fluctuate greatly, thus affecting the performance and fuel economy of the engine.

3. Water leakage in the cooling system: Damage to the thermostat may lead to a decrease in the sealing performance of the cooling system, resulting in coolant leakage. This will lead to the pressure drop of the cooling system, affect the cooling effect, and even cause the engine to overheat.

4. Slow acceleration: If the thermostat is damaged and the engine temperature is too low, it may affect the combustion efficiency of the engine, so that the acceleration performance is reduced and the vehicle power output is insufficient.

5. Abnormal operation of the cooling fan: Damage to the thermostat may cause the cooling fan to fail to work normally, and the engine temperature cannot be lowered in time, thus causing the engine to overheat.

Generally speaking, the damage of automobile thermostat may lead to engine overheating, engine temperature instability, water leakage in cooling system, slow acceleration and abnormal operation of cooling fan. Therefore, once the thermostat is found to have problems, it should be repaired or replaced in time to ensure the normal operation and protection of the engine.