09450-03960 PUMP ASSY, INJECTI Denso Cross

SHUNT COOLING SYSTEM (THERMOSTATS OPEN)Part of the coolant from the left bank is diverted from the block to the oil cooler. External lines direct coolant from the block, to the cooler and back to the return manifold in the front cover.An internal passage in the front cover directs coolant from the return manifold to the thermostats. If the thermostats are closed the coolant flows to the pump and is recirculated through the engine. If they are open, coolant flows from the return manifold to the radiator and from there to the pump. This engine must never be run without thermostats as coolant will not circulate through the radiator and this will cause rapid overheating.By using the shunt cooling system a positive head of coolant is maintained at the pump inlet to help prevent aeration and pump cavitation. It differs from the conventional cooling system in that the radiator top tank is divided into two compartments (upper and lower) with a small air/coolant bleed tube connecting them. A shunt line located as low as possible in the upper chamber connects it to the pump inlet.When the coolant reaches the temperature necessary to open the thermostats, coolant is directed from the bottom of the radiator through the thermostats, water pump, engine, radiator top tank and the radiator core. Coolant (and air which might be in the system) will flow through the small air/coolant bleed tube into the upper chamber. The volume of coolant which flows through the bleed tube from the lower chamber to the upper chamber will flow out the shunt line and to the pump inlet line.Air in the system vents through the bleed tube and remains in the upper chamber until it is vented out through the pressurized relief valve. The top tank temperature must never exceed 210°F (99°C).