826711 9 Mercury NUT, (.250-28)

Service or repair of the engine cooling system must be performed on level ground. The engine must be level in order to check the coolant level. The engine must be level in order to avoid the risk of introducing an air lock into the coolant system.
Drain
Pressurized System: Hot coolant can cause serious burns. To open the cooling system filler cap, stop the engine and wait until the cooling system components are cool. Loosen the cooling system pressure cap slowly in order to relieve the pressure.
Stop the engine and allow the engine to cool. Loosen the cooling system filler cap slowly in order to relieve any pressure. Remove the cooling system filler cap.
Illustration 1 g02513896
Typical example
Remove the drain plug (1) on the engine. Open the drain cock or remove the drain plug on the radiator. Allow the coolant to drain.
Dispose of used engine coolant properly or recycle. Various methods have been proposed to reclaim used coolant for reuse in engine cooling systems. The full distillation procedure is the only method acceptable by Caterpillar to reclaim the used coolant.
For information regarding the disposal and the recycling of used coolant, consult your Caterpillar dealer.Flush
Flush the cooling system with clean water in order to remove any debris.
Clean the drain plugs. Install the drain plugs. Refer to Torque Specifications, SENR3130 for more information on the correct torques.
Do not fill the cooling system faster than 5 L (1.3 US gal) per minute to avoid air locks.Cooling system air locks may result in engine damage.
Fill the cooling system with clean water. Install the cooling system filler cap.
Start and run the engine at low idle until the temperature reaches 49 to 66 °C (120 to 150 °F).
Stop the engine and allow the engine to cool. Loosen the cooling system filler cap slowly in order to relieve any pressure. Remove the cooling system filler cap. Remove the cooling system drain plugs. Allow the water to drain. Flush the cooling system with clean water. Clean the drain plugs. Install the drain plugs. Refer to Torque Specifications, SENR3130 for more information on the correct torques. Fill
Do not fill the cooling system faster than 5 L (1.3 US gal) per minute to avoid air locks.Cooling system air locks may result in engine damage.
Fill the cooling system with Extended Life Coolant (ELC). Refer to this Operation and Maintenance Manual, "Refill Capacities and Recommendations" topic (Maintenance Section) for more information on cooling system specifications. Do not install the cooling system filler cap.
Start and run the engine at low idle. Increase the engine rpm to high idle. Operate the engine in order to open the engine thermostat. An open thermostat will allow any air in the system to be purged. Decrease the engine speed to low idle. Stop the engine.
Maintain the coolant level at the maximum mark that is correct for your application.
Clean the cooling system filler cap. Inspect the gasket that is on the cooling system filler cap. If the gasket that is on the cooling system filler cap is damaged, discard the old cooling system filler cap and install a new cooling system filler cap. If the gasket that is on the cooling system filler cap is not damaged, use a 9S-8140 Pressurizing Pump in order to pressure test the cooling system filler cap. The correct pressure for the cooling system filler cap is stamped on the face of the cooling system filler cap. If the cooling system filler cap does not retain the correct pressure, install a new cooling system filler cap.
Start the engine. Inspect the cooling system for leaks and for proper operating temperature.