Cooling System General Description Cooling System Schematic (1) Cylinder head. (2) Thermostat. (3) Recovery tank. (5) Radiator top hose. (6) Radiator pressure cap. (7) Cylinder walls. (8) Radiator. (9) Radiator lower hose. (10) Water pump. Water pump (10) is installed on the front of the cylinder block. The water pump is driven by a single V belt from the crankshaft pulley. The inlet opening of the water pump is connected to the radiator lower hose (9). The outlet flow from the water pump goes through passages inside the cylinder block. The coolant from the water pump through the cylinder block passages has primary coolant flow to and around the seats for the exhaust valves.
This method gives the coolant with the coolest temperature flow to the hottest area during engine operation. Cylinder walls (7) are cooled by the coolant flow through the block. After the coolant goes through the cylinder block it flows through cylinder head (1) to the thermostat housing, where the bypass type thermostat (2) is installed. The thermostat controls the opening to radiator (8) to control the temperature in the cooling system. If the coolant is cold (cool), the thermostat will be closed. The coolant circulates (makes a complete circuit) from the water pump and through the cylinder block until the temperature of the coolant is warm enough to make the thermostat open.
When thermostat (2) is open the coolant will go through radiator top hose (5) and into the top tank of radiator (8). Coolant then goes through the cores of the radiator. The air from the fan will make the coolant cool as the coolant flows to the bottom of the radiator and out hose (9) where the coolant returns to water pump (10). The radiator is equipped with a shroud to increase the efficiency of the fan and cause the air to be pushed through the radiator and away from the lift truck. If the coolant is hot and the cooling system pressure is too high, some coolant flows to the top of radiator (8) through the tube to recovery tank (3). The cooling system pressure is controlled by cap (6).
When the cooling system pressure goes above its rated pressure, a valve opens in pressure cap (6) which releases the cooling system pressure to the atmosphere. After the engine is at normal temperature for operation, a development of vacuum is present in the cooling system. Pressure cap (6) permits air in the radiator to remove the vacuum at the same time coolant from recovery tank (3) is pulled back into the radiator. G643 (E) Service Manual Chapter 3. Engine Mechanical System 51