If your Volkswagen car has a thermostat issue, the main risk is that your engine could overheat. This is because the thermostat regulates the amount of coolant that flows through the engine. Without a functioning thermostat, your car’s engine could run too hot, leading to serious engine damage and potentially even an engine fire. To avoid the risk of overheating, it is important to have the thermostat checked and replaced if necessary as soon as possible.