You've got a liquid-cooled bike, but do you understand what that liquid does? Take a few minutes to learn about motorcycle coolant.

In an effort to make you a better motorcyclist RideApart tries to answer as many of your questions as we can. Sometimes y'all surprise us with your questions; turns out quite a lot of you want to know about coolant. So, here's everything you wanted to know but were afraid to ask:

Liquid-cooled motorcycles have an extra system that air-cooled bikes don't have, and guess what? It requires maintenance. Over time and with use the coolant becomes more acidic and can begin to corrode and damage the insides of your engine and radiator and water pump. Coolant hoses also deteriorate over time and often crack internally or become soft and bulge, all signs that replacement is needed.

Coolant life varies with the type used and operating conditions. Check your bike's owner's manual for scheduled maintenance recommendations. Generally, standard coolant should be changed about every two years and extended-life coolants should be replaced at around five years.

<em>Be sure to check your hoses and water pump</em>

Be sure to check your hoses and water pump


Coolant is composed of several chemicals, including ethylene glycol, and mixed with water to provide the optimum balance of freeze protection, corrosion resistance, and heat transfer. Even if you live in an area that never has freezing weather, antifreeze-coolant is needed to protect from metal corrosion, to lubricate the water pump, and raise the boiling point.

Radiator pressure caps raise the operating pressure of coolant, which raises the boiling point of the coolant. A system with a working 14 PSI cap and good coolant with a recommended 50-percent/50-percent mixture of water and coolant has a freeze point of around -35 F (-37.2 C). and a boiling point of about 264 F (128.8 C). at sea level. The boiling point deceases at higher altitudes, but it's usually cooler up there, too. Your grandad should have told you this: never open a radiator cap when the engine is hot, it can flash boil and cause severe burns. Allow the engine to cool to the point where you can hold your hand on the radiator before opening the cap.

Cooling systems on modern motorcycles may come in contact with a variety of metals and materials, including iron, steel, aluminum, magnesium, copper, brass, plastic and rubber. The coolant mixture must be compatible with all of these materials. Be sure to purchase coolant-antifreeze which is approved by your motorcycle's manufacturer for use in your engine.

Coolant: Why You Need It and What it Does


Coolant test strips (available in auto parts stores) are a good way to check coolant. If any rust is seen in the system it should be flushed using a flush chemical, then refilled with new coolant of the proper type and mixture. Coolant should also be checked with a hydrometer to measure freeze point protection.

When refilling the coolant, be aware that some systems trap air, which must be bled before the system will operate properly. Look for bleeder screws and check the shop manual for any special procedures. While working on the system, consider replacing the thermostat, which should be changed every five years or more, along with the hoses. When restarting the engine, allow it to idle and warm up fully. Watch the temperature gauge, if equipped, and verify that the coolant is flowing properly and that the electric fan comes on when the engine gets to the temperature this activates (usually above 210 F )

Antifreeze is toxic and its sweet taste is attractive to animals. Therefore, keep it in closed containers and dispose of old coolant properly. Many towns and cities have recycling centers, and it can also be dropped off at many quick-lube shops and auto parts stores.

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