A radiator is a key vehicle component that prevents the engine from overheating.
By regularly flushing the radiator, replacing the coolant and checking the cap, hoses and water pump for leaks or flaws, you can avoid costly repairs and extend the life of your car.
You can do it yourself
Flushing the radiator is the kind of vehicle maintenance job you can easily do yourself.
All you need is a flushing agent, replacement coolant, protective gear for the hands and eyes, and a draining pan or bucket.
You can use a wrench or screwdriver to remove the drain plug located underneath the car.
How often should you flush the radiator?
The general rule is your radiator should be flushed every two years or 100,000 kilometres.
Vehicle makes and models require slightly different maintenance programmes, so we suggest you refer to your owner’s manual for precise information.
What can I use to flush my radiator?
Contrary to what you’ll find on the internet, ordinary flushing agents are neither effective nor good for your car.
The product you use is crucial to the longevity and functionality of the entire cooling system.
Don’t use tap water or any crazy suggestion, like Coca-Cola, that you read about.
Tap water contains minerals that cause corrosive build-up in the radiator.
Professionally formulated radiator flushing products, like Holts Radiator Flush and Radiator Weld, are the best choice.
They remove corrosive build-up, clear water channels and can help seal leaks.
Signs you should flush the radiator
Obvious indications that the radiator needs flushing include:
- steam escaping from beneath the bonnet
- grinding or knocking sounds from the engine
- a visible coolant leak forming under the car
- an overheated engine.
Best practice steps for flushing a radiator
Flushing the radiator is comparatively easy, but we recommend you follow these best-practice steps.
First, inspect the radiator hosts
Ensure the engine is cool to the touch before locating the radiator and expansion bottle. Remove the caps. Inspect the radiator hoses for cracks and wear and tear. Replace them if required.
Drain the radiator
Place a pan or bucket that’s large enough to hold several litres of fluid directly beneath the radiator.
Wearing gloves and safety glasses, carefully remove the drain plug at the bottom of the radiator to allow the fluid to drain into the pan. Pour the drained fluid into a container. Set it aside to be disposed of in an environmentally friendly way. Replace the drain plug.
Flush the radiator
Using a funnel, pour the flushing product into the radiator. Replace the radiator and expansion bottle or reservoir caps. Turn on the engine, together with the heating system, and leave it running for at least five minutes.
Turn off the engine and allow it to cool. Remove the radiator and reservoir caps, plus the drain plug. Allow the fluid to drain. Replace the plug.
Fill the radiator to the “full” indicator with the new coolant.
Bleed the radiator
Bleed the radiator of air by starting the car with the radiator cap off. Leave the engine running for 15 minutes.
Turn off the engine, top up the radiator with coolant and fill the expansion bottle with distilled water. Replace the respective caps. The job is done.
What can happen if you don’t flush the radiator?
If you fail to flush your radiator within the recommended time frame, corrosive sludge and debris can permeate the cooling system.
This can damage the gaskets, other components and cause your car to overheat.
Signs you need a new radiator
If you have flushed your radiator but your car is not running smoothly and there are obvious signs of rust or cracks, it may be time to invest in a new radiator.
It may also be more cost-effective to buy replacement parts (hoses, the radiator expansion bottle or the radiator itself) if:
- the water pump or thermostat fails
- there’s air in the cooling system
- there’s an obstruction in the radiator hoses.