How to Flush and Fill Coolant

Engine coolant, or antifreeze, helps keep your vehicle keep it's cool. This "how to" guide will explain the importance of the job, and the safety steps you need to take.

Learn how you can keep your cooling system in shape by flushing and filling the system.

General steps to flush & fill coolant


Safety first

Park your vehicle on a flat, dry surface and install wheel chocks. Make sure the vehicle has not been running for at least an hour and that the engine and radiator are cool. Be sure to wear safety goggles and protective gloves. Keep coolant away from pets or small children. Clean up any spills immediately. Do not pour coolant down a drain or toilet.


Setting up the job

Open and secure the hood. Inspect the radiator and hoses for any cracks or signs of leaks.
If you notice a worn or damaged hose, it may need to be replaced. Raise your vehicle with a jack and secure the front onto jack stands. Use secure points.


Press down and remove the radiator cap

Carefully press down on the radiator cap and remove it. Make sure the vehicle has not been running for at least an hour and that the engine and radiator are cool. Opening the cap on a hot radiator is extremely dangerous.


Locate the drain plug and loosen

Locate the drain plug. This is found on the radiator. Place a pan under the drain plug to catch old coolant. Loosen the drain plug and allow coolant to flow. Tighten the drain plug when coolant has stopped flowing.


Fill the cooling system with distilled water

Check instructions on flush bottle for specific steps. Steps vary according to flush product.


Install the radiator cap and run the engine

Install the radiator cap and run the engine for 10 minutes with the heater on maximum. Only run the engine outdoors or in a well-ventilated area. Turn off engine and allow radiator to cool. Repeat drain procedure.


Add radiator flush

Add radiator flush. See bottle for specific amount. Top-off with distilled water. Replace radiator cap.


Run the engine

Run engine with heater on max for 10 minutes. Keep an eye on the temperature gauge or light. Allow engine to cool. Repeat flushing process with distilled water until it runs clear.


Close drain plug and install coolant

Check owner’s manual, repair guide, coolant jug or consult an AutoZoner for proper type, ratio (if using 100%) and amount of coolant.


Install cap and clean up

Install the radiator cap. Clean up any spilled coolant and properly dispose of old coolant, water and flush. Disposal laws vary. Check local laws for proper disposal. DO NOT pour coolant down a drain or toilet.

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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