Section 8 - Cooling System - Group 08 Water Pump - Rebuild (8-02) M11 Page 8-17 Visually inspect the bearing retainer rings for nicks or cracks. Assembly Use clean 15W-40 oil to lubricate the drive gear bore and the shaft. Caution: The chamfered side of the drive gear bore must be installed toward the large diameter end of the shaft to prevent damage to the gear when the water pump is installed on the engine. Install the gear in an arbor press with the chamfered side of the gear bore facing up. Insert the impeller end (smallest diameter) of the shaft through the top of the gear bore.