STUD 3D8439 - Caterpillar

Coolant leakage through a damaged precombustion chamber or fuel nozzle adapter and into a cylinder creates a potentially dangerous situation. Rotation of the crankshaft can push coolant out of the cylinder with enough force to severely injure a serviceman.
Through the years, many failures of precombustion chambers and fuel nozzle adapters have occurred on Caterpillar-built Engines. There have been several different types of failures, including pin holes in the bodies of the components and cracked or broken components.
When possible, a serviceman will install a replacement nozzle adapter or precombustion chamber without removing the cylinder head. However, some precautions are necessary to prevent injury to the serviceman during replacement of these components.
If a precombustion chamber or a nozzle adapter cracks or breaks in its threaded area, coolant can enter the cylinder. Coolant in a cylinder creates a potentially dangerous situation for the serviceman. For example, if the top part of the broken component is removed with the fuel nozzle, the bottom part may remain in the cylinder head. This bottom part has an orifice which opens into the cylinder. If coolant has leaked into the cylinder, rotation of the crankshaft by the starter will push the coolant out of the cylinder, through the orifice. The stream of coolant will be propelled with tremendous force, and it can severely injure a serviceman if he is struck.
To prevent personal injury to the serviceman, Caterpillar recommends the use of the procedure which follows to remove broken or damaged precombustion chambers and fuel nozzle adapters.
Do not work in a position that is in line with the broken component. Coolant pushed out of the cylinder through the orifice in the component has tremendous force. The stream of coolant can severely injure a serviceman if it strikes him. To reduce the possibility of injury, the serviceman must use the procedure which follows.
1. Drain the coolant from the engine.2. Remove the broken or damaged component and the fuel nozzle. If part of the broken component remains in the cylinder head, remove the part before any other steps are done.3. Turn the crankshaft by hand through one complete revolution to remove any coolant from the cylinder.4. If necessary, the crankshaft can now be turned by the starter.