990986 Volvo.Penta Lock nut

Illustration 1 g00763105
Cooling System Schematic (1) Temperature regulator housing (2) Radiator (3) Bypass tube (4) Water pump (5) Engine oil cooler (6) Return manifold (7) Supply manifold in the block (8) Cylinder head (9) Cylinder linerThe water pump is driven by a gear. The water pump is located on the right hand side of the engine. The water pump supplies the coolant for the engine cooling system. The coolant is supplied to the following components:
Engine oil cooler (5)
Cylinder head (8)
Cylinder liner (9)
Air compressor (not shown)
Coolant conditioner element (not shown)Note: In air-to-air aftercooled systems, a coolant mixture with a minimum of 30 percent ethylene glycol base antifreeze is recommended in order to improve water pump performance. This mixture keeps the cavitation temperature range of the coolant high enough for efficient performance.
Illustration 2 g00423399
Typical right side of engine (1) Temperature regulator housing (4) Water pump (5) Engine oil cooler
Illustration 3 g00423400
Typical rear of engine (6) Jacket water return manifold
Illustration 4 g00765665
The water pump (4) pulls the coolant from the radiator (2) by using the impeller's rotation. The water pump is located on the right hand side of the front timing gear housing.The coolant is pumped through the engine oil cooler (5). The coolant solution then goes into the supply manifold (7). The supply manifold is located in the cylinder block. The supply manifold distributes the coolant at each cylinder. The coolant then flows around the upper portion of the cylinder liner. The coolant cools the top half of the cylinder liner. At each cylinder, the coolant flows from the jacket water area around the liner to the cylinder head. The cylinder head is divided into single cylinder cooling sections. In the cylinder head, the coolant flows across the center of the cylinder and across the injector seat boss. At the center of the cylinder, the coolant flows around the injector sleeve over the exhaust port. The coolant then exits into the return manifold (6). The return manifold collects the coolant from each cylinder and the return manifold directs the flow to the temperature regulator housing (1). When the temperature regulator is in the closed position, the coolant flows through the regulator. This allows the coolant to flow directly back to the water pump by bypassing the radiator. The water pump then recirculates the coolant. With the temperature regulator in the open position, the coolant is directed through the radiator and back to the water pump inlet.Supply Manifold
Cooling is provided for only the portion of the cylinder liner above the seal in the block. The coolant enters the block from the oil cooler into the coolant manifold which distributes coolant to each cylinder and to each cylinder head. The supply manifold is an integral casting in the block. The coolant flows around the circumference of the cylinder liner and into the cylinder head through a single drilled passage for each liner. The coolant flow is split at each liner so that 60 percent flows around the liner and the remainder bypasses the liner and flows directly to the cylinder head.Temperature Regulator Housing
Illustration 5 g00423402
Front right side of engine (1) Temperature regulator housing (2) Coolant temperature sensor
Illustration 6 g00763133
Temperature Regulator Housing (3) Return manifold (4) Partially opened position of the temperature regulator (5) Closed position of the temperature regulatorThe coolant temperature regulator is a full flow bypass type that is used to control the outlet temperature of the coolant. When the engine is cold, the regulator is in the closed position (4). This allows the coolant to flow through the regulator from the return manifold (3). This allows the coolant to bypass the radiator. The coolant goes directly to the water pump for recirculation. As the coolant temperature increases, the temperature regulator begins to open directing some of the coolant to the radiator and bypassing the remainder to the water pump inlet. At the full operating temperature of the engine, the regulator moves to the open position. This allows all the coolant flow to be directed to the radiator. The coolant then goes to the water pump. This route provides the maximum heat release from the coolant. A vent line is recommended from the manifold to the radiator overflow tank in order to provide venting for the cooling system. The recommended vent line is a #4 Aeroquip.Coolant Conditioner (If Equipped)
Illustration 7 g00423404
Coolant Conditioner (1) Engine oil cooler (2) Outlet hose (3) Inlet hose (4) Coolant flow to cylinder head (5) Engine oil cooler (6) Coolant flow from water pump (7) Coolant conditioner element (8) Coolant conditioner basePitting has been caused by some operating conditions. The pitting has been observed on the following areas:
Outer surface of the cylinder liners
Surface of the cylinder block next to the linersThe pitting has been caused by the following reasons:
Corrosion
Cavitation erosionThe addition of a corrosion inhibitor (a chemical that gives a reduction of pitting) will prevent this type of damage to a minimum. The coolant conditioner element (7) is a spin-on element that is similar to the fuel filter and to the engine oil filter elements. The coolant conditioner element attaches to the coolant conditioner base (8) that is mounted on the engine. Coolant flows from the engine oil cooler (5) through the inlet hose (3) and into the coolant conditioner base. The coolant that is conditioned then flows through the outlet hose (2) into the engine oil cooler (1). There is a constant flow through the coolant conditioner element. The element has a specific amount of inhibitor for acceptable cooling system protection. As the coolant flows through the element, the corrosion inhibitor, which is a dry material, disperses into the