Common cooling problems

Maintaining a stable temperature is critical for your engine. Issues with cooling require quick repairs, but can usually be identified quickly or limited with preventative maintenance.

Common Cooling Problems

Side-by-side comparison of a radiator hose.

1. Coolant leaks and fluid

The most common coolant issue is low fluid caused by a leak. A leak can occur anywhere in the cooling system from a cracked or worn hose and radiator to a leaking water pump seal or heater core. To check for leaks or cracks that aren’t immediately visible, use a pressure tester. The pressure tester forces coolant through the system, making any leaks more obvious.

Person using Blue Devil radiator flush

2. Flush and fill

When was the last time you flushed and filled your radiator? Electrochemical degradation from old coolant and contaminants can weaken the cooling system, leading to corrosion of the radiator and puts hoses, the water pump, thermostat and radiator cap at risk. A coolant flush and fill is recommended every five years or every 100,000 miles. If you’re worried about an issue within this interval, you can use a coolant tester to measure temperature protection.

Side-by-side comparison of an old thermostat vs a new one.

3. Thermostat failure

Thermostats control the flow of coolant into the radiator by changing between ‘open’ and ‘closed’ positions. When they fail, they stick in one of these two positions. If the thermostat fails in the open position, it will allow a continuous flow of coolant into the radiator, causing the engine to run inefficiently and other parts to incur extra wear. In this situation, your vehicle will not be able to reach operating temperature. A few ways to notice this issue are if the temperature gauge hovers around the C marker, if the check engine light comes on, or if the heater is blowing cool or just a little warm, but not hot. If the thermostat fails in the closed position, coolant flow is blocked completely and your engine will overheat. In this case, a dashboard light should surface, you’ll notice the temperature gauge closer to H, staying on H, or jumping to H very quickly while driving, and the thermostat needs to be replaced immediately.

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Be sure to consult your owner’s manual, a repair guide, an AutoZoner at a store near you, or a licensed, professional mechanic for vehicle-specific repair information. Refer to the service manual for specific diagnostic, repair and tool information for your particular vehicle. Always chock your wheels prior to lifting a vehicle. Always disconnect the negative battery cable before servicing an electrical application on the vehicle to protect its electrical circuits in the event that a wire is accidentally pierced or grounded. Use caution when working with automotive batteries. Sulfuric acid is caustic and can burn clothing and skin or cause blindness. Always wear gloves and safety glasses and other personal protection equipment, and work in a well-ventilated area. Should electrolyte get on your body or clothing, neutralize it immediately with a solution of baking soda and water. Do not wear ties or loose clothing when working on your vehicle.

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