2008 Honda Aquatrax ARX1500T3/T3D factory service manual, Page 136Get this manual
COOLING SYSTEM ONE-WAY VALVE CHECK
Remove the left side panel (page 3-7)Remove the band and disconnect the water hoses from the one-way valve to remove it
Shake the one-way valveIt should make clicking or rattling soundApply pressurized water to the inlet port of the oneway valveWater should flow through the one-way valve and out the outlet ports that goes to the engine and exhaust systemApply pressurized water to the outlet portsWater should not flow from the inlet portOutlet Outlet+