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Radiator Flush Additive Explained

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This Review and How To Guide is brought to you by That Car Channel.

An efficient and fully functional radiator and cooling system are critical to the safe operation of any vehicle - especially during the summer months, so when it comes time to replace your coolant, it is worth flushing the system out with a purpose-made cleaning solution. Luckily there are plenty of different coolant flush products available at Supercheap Auto, and they are all used in the same way.

Radiator flush

Why use a radiator flush?

There are a few reasons why you might need to use a radiator flush in order to properly clean out your radiator and cooling system - one of the most common of which is a build-up of gunk that can cause blockages and poor cooling efficiency.

If you have lived with a leaky cooling system for a while, whether due to a faulty gasket, leaking hoses, broken or missing clamps, or even a cracked or damaged radiator, you might have been topping up the system with water. Diluting your coolant in this way can lead to rust forming within the components of your cooling system and will be evidenced by an orange-brown sludge present on your radiator cap, in your overflow bottles and in the top of your radiator.

Another common reason to flush your radiator and cooling system is to remove any contaminants or blockages that can cause your vehicle to overheat and potentially cause more serious problems (such as head gasket failure) in the future. These contaminants can build up rapidly when you have used tap water or bore water to fill your cooling system, so it is critical that you get rid of them before they cause a whole heap of damage.

Alongside maintenance, you might want to switch out the type of coolant you use, in which case you’ll need to flush away any of the old coolant in order to prevent potential reactions or compatibility issues that can occur between the old and new coolant types.

In this video That Car Channel checks out a radiator and cooling system flush and runs us through the process. He uses it to remove a build up of rusty goo in his cooling system after topping his leaky system up with water (before replacing the offending water pump) though it is also simply good practice to flush your radiator and cooling system whenever you replace your coolant.

What is radiator flush?

Radiator and cooling system flushes are generally a type of alkaline salt fluid - they are designed to break down sediments, scale, rust and other undesirable residue that builds up in your vehicle’s cooling system over time. They are harmless to all metals, rubber, plastic and seals used in your motor, and many have the added benefit of neutralising any existing coolant still present, in order to eliminate potential compatibility issues if you decide to switch coolant types.

Flush instructions

What do you need to have on hand before you flush your cooling system?

  • Radiator Flush - You’ll need the right quantity of radiator or cooling system flush fluid. This can be purchased in a few different quantities to suit anything from the home mechanic to workshop use.
  • Coolant - You will need the right quantity of the particular type of coolant that is suitable for your vehicle. Make sure your replacement coolant features the right chemical make-up for your particular vehicle - and if in doubt, ask one of our friendly staff for a hand.
  • Demineralised Water - It’s not advised to simply use tap water when refilling your radiator. Instead, use deionized water, or softened, distilled water if possible.
  • Tools and safety gear - You should always use protective gloves when flushing your radiator, and you’ll also need an appropriately sized tray to catch the old coolant as well as a rag or two in case you spill anything (you will.) You won’t usually need any other tools, although some radiator drain plugs have hex heads instead of taps, while some are super tight and might need to be gently persuaded using a pair of vice-grips or pliers.

Check out the range of required products online or in store at Supercheap Auto, and if you aren’t sure what is right for your vehicle then our helpful staff will always be able to assist.

Pouring in radiator flush

Draining the old coolant

Before you flush your radiator and cooling system you want your engine to be cool. Simply place your drip tray or other suitable container beneath your radiator drain plug, and carefully remove the plug without making a mess or damaging it.

Remove your radiator cap to help the old coolant flow. You might find it easier to drain the system by removing one end of the lower radiator hose - although things can get very messy very quickly, so again, use caution.

Adding your radiator flush

Once all the old coolant mix has completely drained out, replace your radiator plug or hose, and pour the right quantity of radiator flush into your radiator. Smaller bottles of flush will usually require that you add the entire contents of the bottle, although depending on how gunked up your cooling system is, you may want to double the dosage.

Refill the system with water, then pop your radiator cap back on. Some flushes can be used as a sort of “deep clean” - and will require that you keep them in the system for a few days in order for them to break down the deposits and sediments in really neglected motors.

Test radiator

Flushing your cooling system

Start your vehicle and let the motor get up to operating temperature, then turn on the heater and leave your vehicle running for 10 to 15 minutes. This will ensure that the flush works its way through the entirety of your cooling system, and will flush out the contaminants that might have built up in your heater core too.

Switch your vehicle off and allow it to cool for a while, then carefully loosen the drain tap at the bottom of your radiator. This will relieve the internal pressure, and prevent water from potentially bursting out when you open the radiator cap. Carefully remove your radiator cap then drain your cooling system again.

At this point, it might be worthwhile to repeat the entire process with a second flush - particularly if your motor has been left sitting for a while with old coolant in it. It is also important to thoroughly flush the system with clean water a few times in order to remove any of the radiator flush. This will ensure that it doesn’t interact with any new coolant you add.

Refilling your radiator

The flush is complete, so ensure all of your drain plugs, hoses and hose clamps are secure, and refill your radiator with the appropriate coolant and demineralised water - referring to your vehicle’s handbook or workshop manual for information on the correct ratio of coolant to use in your particular vehicle.

Leave the radiator cap off, turn on your engine, and let it run until the radiator bleeds out air. It may take between 15 and 20 minutes for the engine to heat to the proper temperature and begin cycling coolant through.

Replace your radiator cap, dispose of your old coolant and all packaging responsibly, and enjoy a clean, fully-functioning cooling system in the hot days to come!

That Car Channe

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