Section 13.8
Faulty Water Pump

To determine if a faulty water pump is causing high engine coolant temperature, perform the following: ‪

1. Remove the water pump, (gear case mounted) or (gear case cover mounted); refer to appropriate service manual, cooling system chapter.
2. Turn the water pump over and install J–35687 , water pump impeller slip and lash tester, into the tapped holes provided in the impeller; see Figure "Measuring Water Pump Drive Gear Run-out" .
   

   Figure 1. Measuring Water Pump Drive Gear Run-out

3. Clamp the water pump drive gear in a vise, with the impeller facing up. Use soft jaws to prevent damage to the gear teeth.
4. Using a 1/2 in. drive torque wrench in the hole provided in the center of the slip-lash tester, apply 68 N·m (50 lb·ft) torque in either direction. The impeller must withstand 68 N·m (50 lb·ft) torque without slipping.
   1. If the torque 68 N·m (50 lb·ft) is satisfied without the impeller slipping, check combustion gases in coolant; refer to "13.9 Combustion Gases in Coolant" .
   2. If the torque 68 N·m (50 lb·ft) is not satisfied and the impeller is slipping, refer to "13.8.1 Water Pump Impeller Replacement" .

Section 13.8.1
Water Pump Impeller Replacement

Perform the following steps to replace water pump impeller:‪

1. Disassemble the water pump and replace worn or damaged impeller for (gear case mounted) or (gear case cover mounted); refer to appropriate service manual, cooling system chapter.
2. Reassemble the water pump with new components as necessary for (gear case mounted) or (gear case cover mounted); refer to appropriate service manual, cooling system chapter.

Section 13.8.1.1
Test Engine with Repaired Water Pump

Perform the following to determine if thermo-modulated fan replacement resolved high engine coolant temperature:‪

1. Start and run the engine.
2. Run the engine through its operating range with no-load for approximately 5 minutes, allowing the engine coolant to reach normal operating range.
   1. If the engine coolant temperature is 88-96°C (190-210°F), no further troubleshooting is required. Shut down the engine.
   2. If the engine coolant temperature is not 88-96°C (190-210°F), shut down the engine. Check combustion gases in coolant; refer to "13.9 Combustion Gases in Coolant" .