90015-ZW9-000 Honda BOLT, FLANGE (6X18) (Honda Code 6643860).

Illustration 1 g06090818Water temperature regulators are used in each circuit to maintain correct operating temperatures.Jacket Water System
The jacket water pump is on the right front side of the engine. The water pump has a gear that is driven by the lower right front gear group. Coolant from the radiator or the heat exchanger enters the water pump inlet. The rotation of the impeller in the jacket water pump pushes the coolant through the system.The flow of the coolant is divided 3 ways. Some of the coolant from the jacket water pump flows through a tube to the front of the cylinder block and into the main distribution manifold for the water jacket of each cylinder. Some of the jacket water flows through a tube to the aftercooler and then through a tube back to the block and the main distribution manifold for the jacket water of each cylinder. The remainder of the coolant flows through the engine oil cooler.After flowing through the engine oil cooler, this portion of the coolant flows into the water jacket of the right rear cylinder. This coolant is mixed throughout the water jacket with the coolant that flows to the front of the cylinder block.The coolant inside the cylinder block flows around the cylinder liners. The water jacket is smaller near the top of the cylinder liners. This shelf causes the coolant to flow faster for better cooling of the cylinder liner. The coolant is pumped up through water directors into the cylinder heads. The coolant flows through passages around these items in the cylinder head: valves, valve seat inserts, and exhaust outlets.The coolant exits the cylinder heads through tubes and the coolant flows into the water manifold.Coolant flows from the jacket water inlet to block connection into a line for each turbocharger housing. The coolant returns to the water manifolds.Air is vented from the high points of the cooling system. The vent line from the connection must be straight and the vent line must have a slight upward slope. Ensure that the vent is not obstructed.The water manifold directs the coolant to the water temperature regulator housing. The engine has four water temperature regulators. The water temperature regulators control the direction of the coolant flow according to the coolant temperature.When the coolant achieves normal operating temperature, the water temperature regulators open and coolant flow is divided. Most of the coolant goes through the radiator or through the heat exchanger. This coolant circulates back to the jacket water pump. The remainder of the coolant goes through a bypass tube to the jacket water pump.Note: The water temperature regulators are necessary to maintain the correct engine temperature. If the water temperature regulators are not installed in the system, there is no mechanical control. Most of the coolant will take the path of least resistance through the bypass tube. This situation will cause the engine to overheat in hot weather. The small amount of coolant that goes through the radiator in cold weather will not allow the engine to achieve normal operating temperatures. The water temperature regulators control the minimum temperature of the coolant. The radiator or the heat exchanger controls the maximum temperature of the coolant.The bypass tube has another function. When you fill the cooling system, the internal bypass allows the coolant to go into the cylinder head and into the cylinder block without going through the water pump.The total system capacity depends on the amount of coolant in the cylinder block, in the piping, and in the radiator or heat exchanger.Separate Circuit
Illustration 2 g06097436
(1) Auxiliary water pump
(2) Tube for the coolant supply to the aftercoolers second stage
(3) Aftercooler
(4) Tube for the coolant return from the aftercooler to the thermostatic valve
(5) Thermostatic valve
(6) Bypass tube back to pump
(7) Tube for coolant to the radiator or heat exchanger
(8) Inlet for coolant from the radiator or heat exchangerAuxiliary water pump (1) is driven by the engine auxiliary drive. The coolant is pumped through tube (2) to the aftercooler second stage (3). The coolant exits the aftercooler through tube (4) that is connected to thermostatic valve (5).The thermostatic valve has one inlet, two outlets, and a water temperature regulator. When the coolant is cool, the water temperature regulator is closed. The coolant is routed directly back to the auxiliary water pump through tube (6). The coolant is recirculated through the aftercooler.When the coolant reaches the opening temperature, the water temperature regulator opens. The coolant is sent to a radiator or to a heat exchanger through tube (7). The coolant returns to the auxiliary pump through inlet (8).