1999-2004 Honda TRX400EX FourTrax Service Manual, Page 62Get this manual
LUBRICATION SYSTEM
REMOVALINSTALLATlON
Drain the engine oil (page 3-9)
OIL COOLER Disconnect the oil pipes from the oil cooler by removing the joint bolts and remove the O-rings
Remove the two mounting bolts and the oil coolerReplace the 0rings with new ones and coat them with engine oil
Installation is in the reverse order of removal