SHAFT 5M3949 - Caterpillar

Engines:
3606 (S/N: 8RB1-UP)
3608 (S/N: 6MC1-UP)
3612 (S/N: 9RC1-UP)
3616 (S/N: 1PD1-UP)
G3606 (S/N: 3XF1-UP)
G3608 (S/N: 4WF1-UP)
G3612 (S/N: 1YG1-UP)
G3616 (S/N: 4CG1-UP)
Reference: Special Publication, LEKQ7255, "Gas Engines Application and Installation Guide", Pages 38, 43 and 44.In order to achieve optimum service life from water cooled engine components, cooling systems must be able to purge themselves of air. Air in the cooling system can be the result of many factors:
Air can become trapped whenever the cooling system is filled or refilled.
Entrained air can be forced out of the coolant by cavitation in the system.
Combustion gases can leak into the cooling system.For maximum component life, all air must be purged from the water jacket of each engine component. Elimination of air from cooling systems also provides the following benefits:
The possibility of the coolant flashing to steam is reduced.
Coolant additives and coolant conditioners have increased service life.To vent cooling systems, installing vent lines is the preferred method. The vent lines should lead from the highest points in each circuit to the expansion tank. The following high points must be vented:
turbocharger housings
mixer boxes on vee engines
oil coolers on in-line enginesVent lines must travel at a continuous upward slope from the engine to the expansion tank. The vent must enter the expansion tank below normal coolant level. Vent lines should have a diameter of 9.5 mm (0.375 inch) to 12.7 mm (0.500 inch).Because of physical limitations, some installations will not allow vent lines. In these cases, automatic vent valves may be used. Each high point should be connected to a valve that is located 0.61 m (2 ft) to 0.91 m (3 ft) above the highest component.Note: Automatic vent valves require periodic service. The valves must be checked periodically in order to ensure that the valves are not plugged. In addition, coolant may occasionally leak from the vent valves.