Water Pump: Inspection

WARNING: This page is about a different car, the 2003 Subaru Impreza. However, it is still accessible from the selected car via links, so may be relevant.

Check the water pump bearing for smooth rotation.
Check the water pump pulley for abnormalities.
Using a dial gauge, measure impeller runout in thrust direction while rotating the pulley.
1. "Thrust" runout limit: 0.5 mm (0.020 in)
Fig 1: Measuring Impeller Runout In Thrust Direction While Rotating Pulley
Courtesy of SUBARU OF AMERICA, INC.
Check the clearance between impeller and pump case.
Clearance between impeller and pump case:
1. Standard; 0.5-0.7 mm (0.020-0.028 in)
2. Limit; 1.0 mm (0.039 in)
Fig 2: Checking Clearance Between Impeller & Pump Case
Courtesy of SUBARU OF AMERICA, INC.
After water pump installation, check pulley shaft for engine coolant leaks. If leaks are noted, replace the water pump assembly.