Water Pump: Inspection

Check water pump bearing for smooth rotation.
Check water pump pulley for abnormalities.
Using a dial gauge, measure impeller runout in thrust direction while rotating the pulley.
"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 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 And Pump Case
Courtesy of SUBARU OF AMERICA, INC.
After water pump installation, check pulley shaft for engine coolant leaks. If leaks are noted, replace water pump assembly.