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Tech Tips

Coolant Replacement And Bleeding

The following tips will help you change coolant in powersports engines.

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Other than a few cast iron cylinders here and there, the metal that contacts the coolant in powersports engines and cooling systems is mostly aluminum. Cylinder heads, cylinder blocks, water pumps and radiators are all mostly aluminum and therefore, vulnerable to corrosion.

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Because corrosion inhibitors in antifreeze deteriorate over time, most OEMs recommend replacing engine coolant every two years, or 24,000 miles, to prevent corrosion. The fresher the coolant, the less corrosion will build up in the system, and the more efficiently the cooling system will function. The following tips will help you change coolant in powersports engines.

always drain the coolant with a cool engine.1. Always drain the coolant with a cool engine. Remove the radiator cap in two stages. Allow any built up pressure to vent and then open the cap all the way and remove it.

be prepared to replace the sealing washer with the drain bolt.2. There is usually a drain bolt on the water pump. The drain bolt will have a sealing washer, and often the bolt will have a chrome finish. Use the service manual to identify the correct bolt. Remove the drain bolt and sealing washer and allow the coolant to drain into a suitable container. Install the coolant drain bolt with a new sealing washer. Tighten the drain bolt securely.

drain the coolant from the drain points indicated in the service manual.3. Remove the siphon hose to drain the coolant out of the reserve tank. On some models, the reserve tank may need to be removed. Some models may have additional drain bolts for cylinders or radiators, or may even require a coolant hose be disconnected to fully drain the system. Consult the service manual for more information on the particular model’s cooling system.

There are three main types of antifreeze: ethylene glycol (EG), propylene glycol (PG) and organic acid technology (OAT). These types should not be mixed under any circumstance. Flush the system before switching coolant types.

drain the coolant from the reserve tank.4. If the antifreeze is a concentrate, it will require mixing with water before filling. Only use distilled water to mix with antifreeze concentrate. In most cases, the antifreeze to water ratio is 50/50. In cases of extreme cold, the antifreeze concentrate can be increased up to 70 percent of the solution. If the coolant is pre-diluted, it doesn’t require mixing with water before use.

pre-diluted coolant doesn’t need to be mixed with water.5. Slowly pour the new coolant into the radiator filler neck until it reaches the bottom of the neck. Fill the reserve tank to the full line. Consult the service manual for the particular vehicle to find if there are any bleed screws in the system to aid in air bleeding. 

Run the engine with the radiator cap off to bleed air from the cooling system.6. With the radiator cap off, start the engine and let it run for several minutes. Blip the throttle and rev the engine a few times. This will purge any air out of the cooling system. Add coolant to the radiator and the reserve tank as needed. Check for coolant leaks. When the air bubbles stop coming up, turn off the engine and make sure the coolant level is correct.

When the coolant level appears to be correct, install the radiator cap and start the engine. As the engine runs, make sure the coolant system is cycling correctly. The radiator should get warm on both input and output hoses. If a fan is equipped, the fan should eventually cut on. The fan should cut off when the temperature has been reduced to the specified point.

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If the engine has been running for a few minutes and the radiator is not warming, there may be a problem with the thermostat or air in the system. Stop the engine and allow it plenty of time to cool before doing a final coolant level check. Make sure all drain and bleed screws are tight. 

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