DIY! How to Change the Coolant and Clean the Radiator

How to

As a cooling medium for water-cooled engines, a "long-life coolant" called LLC must be used instead of freshwater. Let's recognize this LLC as "the point of cooling parts" that should be replaced regularly.

However, it is also true that many motorcycle owners have continued to ride without exchanging this important coolant, even on the motorcycle that has not been exchanged for years or have been running for the first time in years. In this article, let's check the coolant water in your water-cooled engine and practice the "arrangement = of internal cleaning" before replacement.

Condition barometer is "radiator cap"

Remove the detent that prevents the radiator cap from coming off, and remove the radiator cap counterclockwise to push. If you look at the backside, the coolant is clearly reddish. It is not the color of the red LLC but the occurrence of "rust".

The coolant inside the reservoir tank is rust water!!

The water-cooled engine models that have been immobile for years look roughly like this. On the other hand, if you do not plan to ride for a while and hibernate, you may want to drain all the fuel and drain the coolant. And clearly stated that there is "no coolant".

Drain all the coolant in the reservoir tank, open the drain bolt and drain the coolant inside the engine, insert the water hose into the radiator cap, and pour the water vigorously. Keep the drain bolt of the coolant open.

Rinse until the bright red water becomes "clear"!

When the bright red rusty water turns to clear freshwater, turn off the water supply and tilt the motorcycle body to the left and right to allow the coolant that has accumulated in the cooling passage to drop smoothly. For finishing, set an air gun on the radiator cap and blow air while pressing the cap mouth with waste cloth.

Don't forget to clean the reservoir tank

When it is difficult to see the scale of the reservoir level because it is dyed with rusty water, the coloring of the dirt fades when you soak and wash it by putting detergent in the fuel tank. If the rust stains are too severe, try different types of detergents.


  1. The rusty coolant will damage the engine parts.
  2. If the coolant is drained, rinse the inside of the engine with tap water.
  3. Blow air thoroughly after cleaning the inside of the engine.

If there is a small air compressor, the work efficiency of various maintenance will be greatly improved.

When purchasing an immobile used motorcycle, various "revival" maintenance is essential. I think that there are many cases where the engine can be started by oil change, carburetor cleaning, and cleaning inside the fuel tank, but in the case of "water-cooled engine", be sure to check the condition of the coolant. In this article, I will report on the arrangements before the coolant replacement, but if I consider the full-scale revival of the motorcycle, I will replace the compliment engine radiator cap. Replacing the cooling hose. Replacement of metal pipe parts is also conceivable.

Commercially available coolant is called long-life coolant, generally referred to by the name of "LLC". There is a type that uses a diluted product, and a type that divides the undiluted solution with tap water at a specified dilution ratio according to the riding environment. The liquid color can be green like fluorescent green or red like red wine, but you can use different colors depending on your preference. Many manufacturers sell various types of LLCs, but you can choose your favorite products.

This maintenance motorcycle is a water-cooled model from the '80s. It is a motorcycle that says that it hibernates in the warehouse for more than 20 years though the mileage is low. Various parts of the motorcycle had been damaged and the coolant was a bright red rust color! There was no such thing as LLC anymore.

Race regulations require the use of "fresh water" rather than LLC. For commercial road motorcycle that rides on public roads, don't hesitate to choose an LLC. Since the LLC has a rust prevention effect, it is less likely to damage the internal parts of the engine. Rust occurs if it continues to be used as freshwater, and there is a high possibility that rust powder will be deposited in the impeller shaft of the water pump. Due to the rust, mechanical seals are damaged, and there are many cases where the coolant is mixed into the engine.

When the coolant is mixed into the engine, deterioration speed due to emulsion of the engine oil is significantly increased. If a hand creamy emulsion solid is deposited on the backside of the cap or on the screw when you open the filler cap, first consider that the mechanical seal of the water pump is damaged.

In this article, I have reported on the current status of the coolant and the setup work before the replacement, but when practicing the maintenance, I think you can imagine that there will be a big difference in the condition and the life of the LLC after that whether "done" or "not done" the pre-setup. When the engine oil is changed, it is important to remember that there is an important "set-up" for any work, just as it is more efficient to warm up the engine after starting the engine, and it is possible to extract as much engine oil as even a drop.

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