Routine maintenance is key to keeping your machine on the trails or track longer with less downtime for repairs. The cooling system can often be overlooked at times, but in reality it needs just as much attention as the other moving parts. Without the cooling system working properly, you can experience many different mechanical failures, such as overheating, burst hoses or coolant leaks. For this “How-To” we show you how to replace the radiator hoses, water pump impeller and coolant on a 2008 Yamaha YFZ450, but the steps apply to any liquid-cooled machine. We contacted Boyesen for its SuperCooler kit, along with tough silicone radiator hoses from CV4. We also chose to upgrade the cooling system with an Evans waterless coolant. Evans coolant aids cooling, but most important, it does not boil out of the overflow like a conventional coolant. That helps maintain the coolant volume in tough conditions.
To drain the coolant system you will find the drain plug located on the water-pump cover. This 8mm bolt is removed, allowing the system to drain in a pan. You can remove the radiator cap to relieve pressure for a faster drain. You need to take care at this point to keep the coolant contained. You don’t want to spill the coolant.
With the system drained you can begin to remove the radiator hoses. Most hoses are held in place with spring clamps, and a good set of pliers will help remove these clamps with ease. Some hoses may have worm-drive clamps that require a screwdriver.
Remove the remaining bolts holding the water pump cover. Be careful to not damage the O-ring as you remove the cover. You will need to reuse the O-ring on the new cover. Buying a new O-ring before you start might save headaches later, and they are not expensive.
To remove the water pump impeller you will need an electric or air impact gun. Stick with a small 3/8-inch drive model. You don’t want to resort to brute force that can damage the impeller shaft. This can sometimes be done with putting the engine in gear, but it takes more force.
With the impeller removed, inspect the shaft and seals for any scoring that can cause leakage. Spin the bearings to make sure they spin smoothly with no play, rumbles or grinding sounds. If any of these parts need to be replaced, now is the time to do so.
To install the new impeller you will install the small washer onto the impeller shaft. Tighten the impeller to factory torque specs. Install the new side cover, and torque the bolts to the recommended settings.
Install the new radiator hoses, copying the factory hose routing. Pay particular attention to the clearance around the exhaust system. With the hoses installed and clamped in place you can now begin filling the radiator with fluid. We used an Evans waterless coolant. Evans and other waterless brands require the system to be clean and dry. Normal coolant or water will contaminate it.