Section 8 - Cooling System - Group 08 Water Pump - Rebuild (8-02) M11 Page 8-15 Measure the water pump impeller bore inside diameter. Impeller Bore I.D. mm in 15.339 MIN 0.6039 15.365 MAX 0.6049 Visually inspect the water pump drive gear for broken teeth, cracks or excessive or uneven tooth wear. Measure the water pump drive gear bore inside diameter. Drive Gear Bore I.D. mm in 33.900 MIN 1.3346 33.925 MAX 1.3356 Inspect the seal surfaces of the water pump shaft for large grooves, nicks or damage.