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How to flush a car radiator and clean it

Be flush with success and keep your car running smoothly with these tips.


how to flush a car radiator

Signs you need to clean your radiator:

Find out if it's time to learn how to clean a car radiator by checking for these signs:

  1. Your car keeps overheating.
  2. Coolant is leaking beneath your car.
  3. You hear a knocking noise in your engine.

Even if you take good care of your vehicle, there are going to be parts that just don’t work as well over time. Luckily, you can clean and maintain some of these parts - like the radiator - yourself. Let's start by learning how to clean a car radiator.

Wear rubber gloves to keep your hands clean and safety glasses to stop any fluid splashing into your eyes.

Why is it important to know how to flush a car radiator?

Car running a little hotter than usual? Smoke coming from under the hood? It’s probably your radiator.

A car radiator can become clogged with calcium and rust over time, stopping regular function. This can cause permanent damage to your engine if it goes untreated, leading to costly repairs in the future. Learning how to flush your radiator helps prevent these blockages and any further damage.                                                                                                                 


How to flush a radiator 

Not sure how to use radiator flush products? There are a number of commercial options designed to flush your car's cooling system by getting rid of build-up. They should all have directions printed on their packages but most will work in a similar way to the following steps:

  1. Stop the engine and let it cool completely. 
  2. Place a bucket beneath the radiator - this is to catch any debris and fluid as it comes out of the radiator.
  3. Bleed the radiator by opening the bleed valve.
  4. Close the bleed valve once the radiator has been drained but before adding your flushing product.
  5. Open the cap of your car’s radiator and add the flushing product as directed on the bottle.
  6. Leave the flush in the system and heat it for the time specified on the bottle. This is usually around 10-15 minutes.
  7. Open the bleed valve and allow the flush to drain into the bucket.
  8. Continue to repeat steps 3-7 until the water drains clear.
  9. Flush one last time with distilled water only. Close the bleed valve firmly once finished.
  10. Refill the radiator with coolant.

After flushing your car's radiator, it's best to run the car for a short while to check for leaks. You may also want to take it on a short test-drive locally before making any long journeys.

How to clean a radiator ... with baking soda

Looking for something a little more homegrown? You can actually make a homemade solution to clean a radiator in your car using baking soda!

  1. Start the same way as wtih the commercial product - by cooling your engine and draining all coolant from the radiator.
  2. Mix baking soda with water. You'll want approximately 5 teaspoons of baking soda per 1 litre of water.
  3. Add the solution to your cooling system and run the engine until it’s hot.
  4. Drain the system before flushing it again with distilled water.
  5. Fill with new coolant.

Cleaning your car radiator is just one way you can make sure your vehicle lasts for many years to come. To keep your car working properly and looking its best, check out more of our tips on car care.

Originally published