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DIY: Radiator flushing

Rust and dirt accumulate not only in the engine; your cooling system can also fall victim to this. Regular flushing of the radiator is a vital element that car owners often overlook.

The engine cooling system protects the motor from overheating caused by its operation and makes the engine work within its temperature standards. Regular cleaning of the cooling system from rust and accumulated dirt will help your engine run correctl1y.

Fortunately, the radiator doesn’t need to be flushed as frequently as the oil change is done (it is sufficient to do this every two years). This is a simple job. Simply follow the instructions.

Here’s what you’ll need:

  • new antifreeze (4-8 liters)
  • distilled water (4-8 liters)
  • or ready-made coolant -37°C
  • radiator cleaner
  • drain pan or bucket
  • garden hose
  • a pair of working gloves (waterproof)
  • nylon brush with soft bristles
  • bucket of soapy water
  • safety glasses
  • tanks (cans) for the waste that can be easily resealed (antifreeze is highly toxic and it must be stored and utilized very carefully)
  • absorbent paper towels or cloth for cleaning
  • set of wrenches and screwdrivers

Prior to performing any work, make sure that the engine of your car has cooled down completely. When the engine is hot the coolant in the radiator is under very high pressure!

Clean the radiator

Lift and fasten the hood. Raise and safely support the front end of your car on jack stands. Then, using a nylon brush and soapy water, carefully scrape the dirt off the radiator. Scrape it in the direction of the radiator mounts; otherwise the brittle metal may be damaged. When the radiator is basically clean, jet-wash the radiator with water using a hose to completely wash out all the dirt.
Note: Although the full radiator cleanup should be performed every 2 years, simple washing of the radiator’s outside is best done every 20.000 km.

Place the drain pan

The correct utilization of the used antifreeze is very important. The liquid is highly toxic and has a sweet smell that attracts children and animals. This procedure should not be left unattended, and never drain the waste on the ground. When you have found a suitable tank, place it under the radiator cock.

Check the radiator cap

The radiator cap keeps the antifreeze inside to protect the engine from overheating. The pressure in the system varies depending on the type of engine, it’s written on the cap. The radiator cap consists of a spring ring attached between the flat metal top and a small rubber attachment at the bottom. The tension between the spring and the rubber ring is what helps the cap to keep the pressure. So if the spring easy to compress, then it's time to replace the cap. Another sign that the filler cap is worn is rust on the clamp. In short, the cap should be replaced at least every 2 years, so you can do it at the same time with the cleaning of the radiator. Remember that there are different caps for different pressures.

Check the clamps and hoses

The next step is to check the radiator clamps and hoses. There are 2 hoses: one on top of the radiator, it brings the hot liquid out of the engine, the second is at the bottom, and it brings the cold liquid into the engine. To replace the hoses, the radiator must be dried, so check them before you begin. If you see that the hoses are cracked or leaking, or the clamps are covered with rust, you can replace them before filling the radiator.

Remove the remains of the old fluid

The radiator drain cock usually has a handle so it is easy to open. Unscrew the valve (do not forget about the gloves – the coolant is toxic!) and let the liquid leak in the tank under the car. Remove the radiator or coolant tank cap to let it drain faster. When all the liquid is spilled, close the valve and pour the waste into the tank prepared in advance. Then place the pan back under the radiator cock. Now everything is ready for flushing.

Flush the radiator

Variant 1
Take your garden hose, direct the jet of water into the radiator and let it fill up. Then open the drain cock and let the water completely run out into the pan below. Repeat until the water is clear, and make sure that all the used water is also in the tank the same way as the used coolant. If necessary, replace all worn hoses and clamps.

Variant 2
Use this option in case of heavy pollution of the cooling system or when you are not sure of previous service (for example, when buying a used car). Pour the contents of the radiator cleaner in the radiator. Start the engine and let it idle for 15-20 minutes to ensure proper penetration of the chemical into the cooling system. Empty and flush the cooling system by opening the drain cock when the engine is running.

Add the coolant

Use a ready-made coolant, such as FREEZANTE LongLife or Extra. An important thing you should look for at the label when buying is the international standard sign or icon. Why? You can read about this in one of our publications. Most radiators have the capacity of no more than eight liters of liquid, so it is better to determine the amount you need in advance.

Remove the air out of the cooling system

Now you should remove air-locks, which may appear in the cooling system. Start the engine with the radiator cap is open (to avoid high pressure) and let it idle for approximately 15 minutes. Repeatedly squeeze the thick radiator hoses with your hand until you feel that there is liquid inside. Then turn the heater control up to the maximum. These actions will force the coolant to circulate and the air to disappear. When the air locks are removed, the volume they occupied is released for a small amount of coolant you can add. Be careful, the air coming out of the radiator can be very hot. Then just close the cap and wipe off any excess liquid with a cloth.

Check for any leaks or splashes out of the drain cock, utilize the clothes and the coolant package. Now you are almost ready to go. It is also important to properly utilize the used antifreeze, do it very carefully. Again, the smell and the color of the cooling fluid attract kids, so don't let them close for a long time. Take the tanks with the waste to the nearest recycling center.


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