Common reasons that can cause a motor radiator problem

  • A failed thermostat. The thermostat is the most common culprit when a vehicle overheats. The thermostat isn't actually part of the radiator itself, but a type of valve that controls how much coolant can flow into and out of the radiator. This helps keep the engine at optimum operating temperature. When the thermostat fails, the car begins to overheat very quickly.

  • Leaky radiator hoses. The most common source of a leak within the cooling system isn't the radiator, but the radiator hoses. The hoses link the radiator to the engine and allow coolant to flow between the two. Radiator hoses are considered to be a wear component, which means that they should be replaced periodically, whether they are working well or not. That's because they tend to become more prone to failure over time.

  • Air in the cooling system. Air can become trapped in the cooling system, which restricts the flow of coolant and reduces its efficiency. If your car seems to be running hot, you might want to see about having the cooling system bled to remove possible air bubbles.

  • Radiator leaks. Leaks in the radiator itself are harder to locate and repair than problems with hoses. Look for bubbles or steam coming from the radiator to signal the location of a leak. Leaky radiators can sometimes be patched, but it's a tricky job.

  • A failed water pump. The cooling system uses a pump to move the coolant throughout the engine in order to regulate the temperature. Water moves through the radiator, past the pump, into the engine and then is forced back into the radiator. If the water pump fails, the water no longer circulates properly and the car will overheat. A broken water pump is fairly common.

  • Cooling system obstructions. Obstructions can take the shape of engine "scale" blocking the cooling passages in the engine or radiator, which makes it difficult for coolant to move efficiently. Obstructions can also happen when something restricts the flow of air through the radiator, which in turn makes it hard for the radiator to transfer heat to the air. This can be caused by anything from bent fins to body damage from an accident.

  • A failed radiator fan. Modern cars use an electric fan to pull enough air through the radiator to keep the car cool at idle and low speeds. A car that does fine on the freeway but overheats at idle or in traffic probably has a problem with the radiator fan.