970944 Volvo.Penta Hexagon screw

The engine is cooled by forced circulation of coolant by the water pump.The illustrations show the coolant flow. (1) Water PumpOf a centrifugal type, the water pump is driven by the V-belt from the crankshaft pulley.A unit seal is installed between the impeller and water pump that prevents leakage of coolant. There is a drain hole provided at the bottom of the water pump case, which ensures that water, should it leak from the unit seal, does not enter bearings. On 4D3, the water pump is mounted on the timing gear case provided with a suction pipe and swirl chamber.Pressed into the one end of water pump shaft is the impeller with backward blades which feeds coolant under pressure into the engine. On 4DR5, the water pump is installed at the front of crankcase.An impeller with combination-type blades is press-fitted into one end of the water pump shaft.An integral bearing unit is used combining a needle roller bearing and ball bearing. It is nonmaintainable. (2) Thermostat The thermostat, of a bottom bypass configuration, has a valve controlled by a special wax enclosed in a pellet. The wax changes from solid to liquid as it is heated, involving volumetric change for regulating the flow of coolant.The changes in valve position with varying coolant temperatures regulate the flow rate of coolant into the radiator and water pump (bypass side), thus controlling coolant temperature. A jiggle valve is provided in the air purge hole of the thermostat to quickly increase the coolant temperature, thereby providing earlier heating.The jiggle valve is in down position by its own weight when the engine is stationary. So, when pouring in coolant, the air in the system is forced into the radiator through the clearance between the air purge hole and jiggle valve.When the engine is started, coolant circulates and the jiggle valve is forced upward by the hydraulic pressure.As a result, the valve closes the air purge hole, preventing outflow of coolant through the air purge hole. (3) Radiator The radiator cooling capacity varies depending on applications (installation in an enclosed generator room of a building, operation in stationary state, etc.). Considerations are, therefore, paid to the fan diameter, radiator capacity and other factors. Some units for construction plants are equipped with an oil cooler to cool hydraulic oil. * Pressure increasing When the pressure in the radiator exceeds the specified level, the pressure valve opens against the pressure spring to allow inside air to escape to the atmosphere, thereby decreasing the pressure.* When at negative pressure When the coolant temperature drops and a negative pressure develops inside the radiator, the vent valve opens to insert air, thereby preventing deformation of the radiator.The pressure in the cooling system can also be reduced by pulling up the pressure reduction lever.2. Specifications
3. Service Standards
3.1 Service Standard Table
3.2 Tightening Torque Table
4. Special Tool
5. Service Procedures
5.1 Cooling Fan
Removal and Installation
5.2 Water Pump
Removal and Installation
Disassembly and Inspection
Disassembly and Inspection(1) Removal of Flange Remove the flange using a gear puller.(2) Removal of Impeller Remove the snap ring. Using a press, remove the water pump shaft together with the ball bearing.Remove the impeller.Heating the water pump case to about 80°C helps the operation.(3) Replacement of Unit Seal (a) Check the unit seal installed in the impeller and water pump case for damage and water. Remove and replace the unit seal if faulty or water leaks during operation. Be sure to replace the unit seal with a new one if removed.<Replacement of Unit Seal Only> (b) To replace unit seal only, tap M8 x 1.25 threads in the two holes of the impeller. Install Water Pump Impeller Puller (special tool) through the holes and remove the unit seal.(4) Tightening Interference between Impeller and Water Pump When the impeller is removed from the water pump case assembly, it may result in insufficient interference. Reassembly should therefore be limited up to two times. If the specified interference is not obtained even at the first or second reassembly, the impeller must be replaced with a new one.(5) Removal of Ball Bearing Using a gear puller or a press, remove the ball bearing. Do not remove the water pump snap ring. (1) Remove the flange with Puller (special tool) or gear puller. (2) Remove the wire. (3) Tap two holes in the impeller to M8 x 1.25 and, using Water Pump Impeller Puller (special tool), remove the impeller. (4) Using a press, force the bearing unit out. Heating the water pump case to about 80°C makes the job easier. Keep the removal load of the bearing unit within 1 000 kg. (5) When the impeller and flange are removed from the bearing unit, it may result in insufficient interference. If they are disassembled more than two times, or if the interference is below the specification even reassembly is two times or less, they must be replaced with new ones. Measure the interference between the impeller and bearing, and between the flange and bearing unit.Reassembly
(1) Installation of bearing unit Apply load to the outer race of the bearing unit and press the bearing unit until the outer race is flush with the water pump case end face. 1. Check that the bearing unit rotates smoothly before installation.2. Do not press the bearing unit shaft end face.(2) Installation of the wire Align the groove in the water pump case with that in the bearing; then, insert the wire into the wire insertion slot.(3) Installation of the unit seal To install the unit seal, use the Water Pump Unit Seal Installer (special tool). Press it into position until the dimension shown is reached.(4) Installation of the impeller Using a press, press-fit the impeller into position. Let the end face of the shaft on the flange side of the bearing unit receive the press-fitting load.(5) Clearance between impeller and case Check if the clearance is up to specification.(6) Installation of the flange Press the flange into position until the distance between the flange en