How the Cooling System Works and How to Maintain It

Your vehicle's cooling system keeps your engine from burning up from its own heat by pushing coolant that is cooled in the radiator through passages on the engine block and head. The system is somewhat more complex than that, with power transferred from the serpentine belt to the water pump to keep the system moving. That's why we have pulled together a list of parts to check on your cooling system.

Take Care of Your Cooling System

Cooling system failure is the number one reason for engine related breakdowns. Your cooling system works hard to prevent your engine from overheating, or freezing up. That’s why it’s so important to keep it maintained properly. It’s not hard to keep it in tip-top shape, and AutoZone has everything you need, including trustworthy advice, to help you do the job right. See the diagram above and tips below to start protecting your engine today.

8 Cooling System Parts You Should Check Regularly

1. Accessory Belts Drive the Cooling System

Whether your car has V-belts or a serpentine belt, the belt transfers power from the engine’s crankshaft to the water pump to power the cooling system. Inspect belts to make sure they are not loose. Also, look closely for cracking, fraying or excessive rib-wear.

2. The Water Pump Pushes Coolant Through the System

In order for the system to work, the coolant needs to move throughout the system. The water pump uses power from the crankshaft and serpentine belt to force coolant into the engine and through the rest of the cooling system. Allow your engine to run for a few minutes before inspecting your water pump. Visually check for leaks around the unit. Failure of your passenger compartment to heat properly can also indicate a faulty water pump.

3. The Heater Core Helps Adjust Cabin Air Temperatures

The heater core is where the engine cooling system meets the cabin AC system. The core is where heat from the engine warms up cabin air, which also helps the coolant lose some heat before returning to the radiator to be cooled again. Inspect for signs of leakage indicated by fluid around the heater core or wet spots on your carpet. Constant presence of fog on the inside of your windshield can also mean that your heater core needs replacing.

4. Heater and Radiator Hoses Carry Coolant Through the System

Coolant hoses direct coolant between the other parts of this system. Make sure all hose connections are secure. Inspect for swelling, cracking and fraying. Also, make sure there are no collapsed or soft sections. Always check hoses while engine is cool.

5. Cooling Fans Move Air Past the Radiator to Prevent Overheating

Radiator fans increase airflow to help the system cool more efficiently. Make sure all blades on your cooling fan are in good condition and not damaged. A noisy fan blade is a good indicator of damage.

6. Coolant Temperatures are Measured by the Thermostat Before Returning to the Radiator

The thermostat measures the temperature of coolant before it comes back to the radiator. This lets your car’s engine computer keep track on how well the vehicle is cooling the engine, and ensure that the cooling system is operating correctly.

7. The Radiator Exchanges Coolant Heat with Outside Air

As coolant flows through the radiator, cool air blows past the radiator, cooling the coolant before it is recirculated through the engine. Check your radiator fluid for the proper concentration in the coolant reservoir. Consult your owner’s manual for the location of your reservoir. Most manufacturers recommend 50% antifreeze and 50% water mixture. Make sure the fluid reaches the “Full” line. If not, pour in enough antifreeze to reach the line. An AutoZone store associate can help you find the right antifreeze for your vehicle.

8. The Radiator Cap Allows for Easy Filling

The radiator often acts as a reservoir for coolant, and this cap seals the system while providing easy access for when more coolant needs to be added. Make sure your radiator cap is always tight and secure so that it seals properly. Never remove it when the engine is hot. Here are some guidelines on when you should replace your radiator cap:

  • Radiator caps can deteriorate after 40,000-50,000 miles
  • As a general rule, radiator caps should be changed when a thermostat, water pump or radiator is replaced. This will ensure the system is operating at the proper pressure

Flushing and Filling is Easy as 1-2-3!

Remember to flush and fill your radiator every 24 months or 24,000 miles.

  • Drain your cooling system
  • Flush with water and a quality flush product
  • Fill with 50%-50% or 70%-30% antifreeze water mixture. Use more antifreeze if you drive in extreme temperatures

Stop by your local AutoZone store for more helpful advice and everything you need to do the job right. Find an auto parts store near you.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

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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