1. Install the radiator pressure tester on the deaeration tank and run engine at elevated idle. Monitor the pressure in the system using the tester gauge to see if pressure rises above normal value of deaeration tank cap.
• If pressure is higher than the pressure rating of the cooling system cap, go to “Combustion Leaks to Coolant” (page 102) in this section.
• If pressure gauge reading is below pressure rating of system, replace the thermostat.
