Will a engine overheat without a thermostat?

Yes, an engine can overheat without a thermostat. The thermostat regulates the flow of coolant to maintain optimal operating temperature; without it, the coolant may not circulate properly, leading to inefficient cooling. Additionally, the engine may not reach its ideal temperature quickly, which can also cause overheating under certain conditions. Overall, the absence of a thermostat disrupts the cooling system's balance, increasing the risk of overheating.