DIY

How to Flush Coolant

Reading Time: 4 minutes

Nearly every vehicle manufacturer recommends a coolant flush as part of their maintenance schedule—it’s an essential part of any car care routine. Why? Because coolant breaks down over time and becomes acidic. And when that happens, it can eat away at the various metal components found throughout the engine and cooling system.

Many late-model vehicles have organic additive technology (OAT) coolant that lasts longer than traditional, green inorganic additive technology (IAT) coolant. Still, even these more advanced formulas require a periodic flush or exchange.

The good news is, with the right tools and a little know-how, you can easily do a coolant flush at home.

antifreeze
Be careful when handling coolant because it contains toxic substances.

How to Do a Coolant Flush

Most professional repair shops use a dedicated machine to perform coolant flushes—but you can use a bottle of radiator flush/cleaner to do a similar job at home.

Are you ready? Good! Let’s get started!

Tools Needed for a Coolant Flush:

The tools needed to do a coolant flush will vary, depending on what type of car you have. In general, however, you’ll need:

opening radiator cap
Make sure the engine is cool before opening the radiator cap.

Coolant Flush Instructions:

Before we begin, keep in mind: all vehicles are different. The information below is generic and for entertainment and educational purposes only. Be sure to follow the repair information for your specific application.

Repair manuals, such as those from Chilton, are useful, but a subscription to a repair database is even better. ALLDATA and Mitchell 1 both have single-vehicle subscriptions for DIYers that provide detailed factory repair information.

You can learn more about accessing quality repair information in this article.

pouring coolant into the radiator
Top off the coolant as needed and reinstall the radiator cap.

Now, let’s get down to flushing your coolant. Here’s how it’s typically done:

  1. Put on your safety glasses.

  2. Make sure the engine is off and cool.

    Warning: Hot coolant can cause severe personal injury. Make sure the engine is cool before proceeding.

  3. Safely raise and support the vehicle using a jack and jack stands. Set the parking brake and chock the rear wheels.

  4. Place a fluid catch pan under the vehicle.

  5. Remove the radiator cap.

  6. Drain the old coolant. You can do this by either disconnecting the lower radiator hose (recommended) or by opening the radiator drain petcock. Disconnecting the lower radiator hose is the safest route since petcocks can become brittle and break.

    To disconnect the lower radiator hose:
    -Make sure the fluid catch pan is under the lower radiator hose.
    -Use a pair of pliers or a screwdriver (depending on the clamp design) to loosen the hose clamp.
    -Wiggle the lower radiator hose while pulling it toward you to disconnect it from the radiator.
    -Allow the coolant to drain into the fluid catch pan.

  7. Reinstall the lower radiator hose and tighten down its clamp.

  8. Follow the instructions on the flush/cleaner you’re using to add the correct mixture of flush and distilled water to the radiator.

  9. Follow the instructions on the product to run the flush through the cooling system.

  10. Wait until the engine has cooled down completely.

  11. Place the fluid catch pan under the vehicle.

  12. Disconnect the lower radiator hose (as outlined earlier) to drain the flush mixture from the cooling system.

  13. Reinstall the lower radiator hose and tighten the clamp.

  14. Safely remove the jack stands and lower the vehicle.

  15. Follow the instructions that come with the cooling system vacuum fill tool to connect the tool to your air compressor. The tool bleeds the cooling system of air while simultaneously refilling the coolant.

  16. Follow the instructions that come with the tool to refill the cooling system with a 50/50 mix of fresh coolant.

  17. If you do not have access to an air compressor and vacuum fill tool, consult a repair manual or repair database for the cooling system bleeding instructions for your vehicle.

    Warning: If you do not properly bleed the air from the cooling system, overheating and engine damage may result.

  18. Top off the coolant as needed and reinstall the radiator cap.

  19. Make sure the vehicle doesn’t overheat by starting the engine and monitoring the temperature gauge. Do this until the engine reaches operating temperature, and the cooling fan kicks in.

  20. Pour the old coolant and flush from the catch pan into a large fluid container.

  21. Make sure to clean up any fluid spills with a rag. Coolant is deadly if consumed, and animals are attracted to it.

  22. Check online to find out where you can recycle your old coolant (pouring it down the drain is illegal). Usually, you can get rid of it at a landfill that accepts hazardous waste.

  23. After driving the vehicle for a day or two, re-check the coolant level and top off as needed.

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Author

Mia Bevacqua

Chief Mechanic at CarParts.com

Mia Bevacqua is an automotive expert with over 15 years of industry experience. She holds ASE Master, L1, L2, and L3 Advanced Level Specialist certification, as well as a bachelor's degree in Advanced Automotive Systems.

Throughout her career, Mia has applied her skills toward automotive failure analysis inspections, consulting, diagnostic software development, and of course, freelance writing. Today, she writes for companies around the world, with many well-known clients showcasing her work.

Mia has a passion for math, science, and technology that motivates her to stay on top of the latest industry trends, such as electric vehicles and autonomous systems. At the same time, she has a weakness for fixer-upper oddballs, such as her 1987 Chevy Cavalier Z-24 and 1998 Chevy Astro Van AWD.

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