ADAPTER 4488999 - Caterpillar

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.
Check the coolant level when the engine is stopped and cool.
When any servicing or repair of the engine cooling system is performed, the procedure must be performed with the engine on level ground. This procedure will allow you to check accurately the coolant level. This procedure will also help in avoiding the risk of introducing an air lock into the coolant system.
Remove the cooling system filler cap slowly in order to relieve pressure.
Maintain the coolant level at the maximum mark that is correct for your application. If the engine is equipped with a sight glass, maintain the coolant level to the correct level in the sight glass.
Illustration 1 g02590196
Typical filler cap gaskets
Clean the cooling system filler cap and check the condition of the filler cap gaskets. Replace the cooling system filler cap if the filler cap gaskets are damaged. Reinstall the cooling system filler cap.
Inspect the cooling system for leaks. Note: The Diesel Exhaust Fluid (DEF) tank requires coolant flow around the tank. The Coolant Diverter Valve (CDV) will turn the flow on or off. If the coolant system has been filled with the CDV in the closed position, coolant level will drop because of the opening of the CDV. The coolant flow will be diverted when the ambient temperature is approximately −5° C (23° F).