NUT-HEX SLOTTED 2405084 - Caterpillar

Clean the cooling system and flush the cooling system before the recommended maintenance interval if the following conditions exist:
The engine overheats frequently.
Foaming is observed.
The oil has entered the cooling system and the coolant is contaminated.
The fuel has entered the cooling system and the coolant is contaminated.
Use of commercially available cooling system cleaners may cause damage to cooling system components. Use only cooling system cleaners that are approved for Caterpillar engines.
Note: Inspect the water pump and the water temperature regulator after the cooling system has been drained. This is a good opportunity to replace the water pump, the water temperature regulator and the hoses, if necessary. 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.Note: Refer to Operation and Maintenance Manual, "General Hazard Information" for information on Containing Fluid Spillage.
Open the cooling system drain valve (if equipped). If the cooling system is not equipped with a drain valve, remove one of the drain plugs.Allow the coolant to drain into a suitable container.
Properly dispose of the drained material. Obey local regulations for the disposal of the material.
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.
Flush
Flush the cooling system with clean water in order to remove any debris.