>> A << O-Ring Installation
WARNING: This page is about a different car, the 2003 Mitsubishi Outlander. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
Do not allow engine oil or other grease to adhere to the O-ring
Insert the O-ring to the water pipe, and coat the outer portion of the O-ring with water or engine coolant.
Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.