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How to Flush a Radiator: The Complete Guide

Make This Easy Five-Step Process Part Of Your Regular Car Maintenance Routine

Flush Your Coolant

How to Flush a Radiator

Flushing your radiator is an important part of regular car maintenance. It helps keep your car in top-notch condition. Radiator fluid or coolant helps keep your car engine running well. But sometimes antifreeze can build up as old coolant, rust, and scale deposits. If this build-up is left too long, it can damage the radiator and lead to costly repairs.

Flushing the radiator is one of the only ways to remove this build-up. You should flush your radiator at least once a year. There are several signs to look for to know when it’s time to clean it. Let’s look at how you can flush your radiator yourself, signs it’s time to, and best methods for flushing it.

1. Look For Signs of Build-Up

There are several signs that indicate you need to flush your radiator. The most common one is an overheating engine. If you notice that the engine is running hotter than it should right after you start the car, it’s probably time to flush the radiator. Some other signs to watch for include if you spot a coolant leak (look for green or orange fluid pooling under your car) or if you can see debris in your coolant. Irregular smells, like a hot maple-syrup-like smell or the smell of antifreeze, can also indicate you need to take a look at your radiator. Lastly, any grinding or knocking engine noises or steam coming from under the hood could also indicate a problem with your radiator.

2. Gather Supplies

Flushing your radiator is a fairly easy process that doesn’t require a long list of supplies. However, having a few items on hand will make the process go even smoother. We recommend the following:

3. Drain The Coolant

Once you’ve determined that you need to flush your radiator and gathered the appropriate supplies, the next step is to drain the coolant from the radiator. Make sure that your car is off and the engine is cool because the coolant can be extremely hot and can scald you.

The first step is to locate the coolant reservoir cap and unscrew it as this will help the radiator drain more easily. Next place your pan under the radiator drain to catch the dirty fluid. Once you’ve opened the reservoir cap, open the drain to let all of the antifreeze out.

Be sure to check with your local authorities on how and where to safely dispose of old fluid.

4. Use Radiator Flush

Once the old coolant is drained, pour in your choice of radiator flush. Follow the directions on the flush because there are a lot of different options on the market and each one has slightly different directions. Two of the more popular and effective flushes are Thermocure Coolant System Rust Remover and Super Radiator Flush.

The process is fairly universal, but some things can vary so, again, be sure to read the directions. The basic process is to put in the flush, turn on the engine to circulate the fluid, let the car cool, and then drain the flush. You can repeat the process if necessary.

Be aware that these and all flushes are corrosive and can harm most things they touch, like rubber seals or painted surfaces. Make sure you wear protective gloves and safety glasses when handling all flushes and be aware that some flushes should not be used on certain metals. If the flush and the metal of your radiator are incompatible, the flush will do more harm than good.

5. Refill Coolant

Coolant pouring into car

After draining the flush, run distilled water through the radiator until it is clear in order to rinse out any excess flush. You may need to turn on the car again to circulate the fluid. If you do, make sure you let the car cool before draining this final batch of fluid.

After you have cleared out all of the water and flush, refill the antifreeze to the appropriate level, and you’re ready to go!

Steps For How To Flush A Radiator

  • 1. Look for Signs of Build-Up
  • 2. Gather Supplies
  • 3. Drain Coolant
  • 4. Use Radiator Flush
  • 5. Refill Coolant




Frequently Asked Questions

Can you flush a radiator with a garden hose?

You can flush a radiator with tap water, but it won’t be as effective as using a flush. The flush has corrosive properties that will actually get all of the old antifreeze, rust, and scale cleared out. And while you can use water from a garden hose to flush the system, it is recommended to use distilled or de-ionized water for your final flush or for mixing with antifreeze.

How long does a radiator flush take?

The time required for a radiator flush depends on the type of flush you use and the time it takes for your car’s engine to cool down completely. Some of the flushes take longer than others. Usually, it takes anywhere from 30 to 60 minutes to flush a radiator.

Are there different types of radiator flush?

There are a couple of different types of flushes. The two most common are powder and liquid. They both are effective and can clean your radiator, but they both pose different problems.

Powder flushes have more inherent health risks. You can accidentally breathe it in or it spreads to the skin and it causes chemical burns. Powder flushes are powerful but have more risks associated with their use. Liquid flushes are also caustic, and you will need to take the proper precautions to guard against spills and splashes.

What should I do if I’m still experiencing problems?

If you’re still experiencing problems with your cooling system, you can try to do a second flush or take it into a professional. Sometimes the buildup in the system is too much for a flush at which point you will need to seek professional help.



Haley Butterfield
About Haley Butterfield

Haley is a writer, reader, and life long learner. She recently graduated from Brigham Young University and enjoys spending time with family and friends. In her free time, you can find her reading the latest book, discovering new hobbies, or running in the desert.