Coolant Flow

Information about coolant flow in the raw water cooled or engines with a closed cooling system is located in the “cooling system”section of the current engine mechanical workshop manuals.

The picture above shows a raw water cooled 8.1L. The other engines are similar.

Raw water is pulled into the pump (11) through the drive and thepower steering cooler (22). Raw water is then discharged from the pump to the thermostat housing (12). If the thermostat is closed (as in D above), water goes through a cast bypass (C) inside the thermostat housing and is sent to the exhaust risers (18) and then overboard in the exhaust. If the thermostat is open (as in B above), then the raw water issent to the circulating pump (15), into the block (16), up through the heads (17) and back tothe thermostat housing (12) under the thermostat. It then travels through the open thermostat, into the riser bypass hoses and then overboard.

In both the raw water cooled systems and the closed cooling systems (antifreeze), the fuel cell (MOAS) is RAW water cooled. Water flow through the fuel cell is from the thermostat housing nipple (8) to the bottom of the fuel cell, through the cell, out the top of the fuel cell and over to one of the exhaust risers and then overboard. The fuel cell has a second hose on top of the cell that goes to the intake manifold. This is thehigh pressure pump reservoir vent line. Engine vacuum pulls the vapors off the top of the cell and into the engine intake system to be burned. The hose connects to a pulse limiter at theintake manifold. The pulse limiter prevents a backfire of the engine from igniting the fuelvapors in the hose.