Water Lines Group
(2) Water temperature regulator housing. (3) Bypass hose. (6)
Water pump. (8) Outlet (to radiator). (9) Water temperature
regulator (shown partially open). (A) Heater supply (two ports).
(13) Pump outlet pressure (alternate heater supply). (14) Port
(water supply to aftercooler, if equipped). (15) Water pump
inlet, two ports (heater return). (16) Alternate pump out
pressure (for engine diagnosis).
From the cylinder block, the coolant flows into passages in the
cylinder head. The passages send the flow around the unit
injector sleeves and inlet and exhaust passages. The coolant
now enters water temperature regulator housing (2) at the front
right side of the cylinder head.
Water temperature regulator (9) controls the direction of flow.
If the coolant temperature is less than normal, the water
temperature regulator is closed. The coolant is directed
through bypass hose (3) and into the top inlet of the water
pump. When the coolant gets to the correct temperature,
water temperature regulator (9) opens. Most of the coolant
goes through outlet (8) to the radiator for cooling. The
remainder flows through bypass hose (3) and into the water
Water temperature regulator (9) is an important
part of the cooling system. It divides coolant flow
between the radiator and the bypass as necessary
to maintain the correct temperature. If the water
temperature regulator is not installed in the
system, there is no mechanical control, and most
of the coolant will take the path of least resistance
through the bypass. This will cause the engine to
overheat in hot weather. In cold weather, even the
small amount of coolant that goes through the
radiator is too much, and the engine will not get to
normal operating temperatures.