12 Cooling System - Perkins 900 Series Workshop Manual

900 Series
12
Cooling system 12
General information
Note: Refer to the "Cooling system flow diagram" on page 196 for illustration references.
Coolant (A4) from the bottom of the radiator passes through the centrifugal coolant pump, which is fitted onto
the front of the timing case to assist the flow of the coolant through the system.
The pump is driven by a "V" belt from the crankshaft pulley.
From the pump, the coolant passes through a rubber hose to a passage in the left side of the cylinder block
and to the inlet of the cassette type oil cooler. The coolant passes through the oil cooler and is returned to the
inlet side of the centrifugal coolant pump.
The coolant (A6) passes from the passage to the cylinder block through two holes in the cylinder block casting.
The coolant then passes around the cylinders and up into the cylinder head through a series of large holes. A
small hole at the rear of the cylinder block ensures that there are no air pockets.
The coolant leaves the cylinder head at the front and passes through a short hose into the thermostat housing.
When the engine is cold the thermostat is fully closed (A1) and the coolant (A5) goes directly through a by-
pass valve in the thermostat to the inlet side of the coolant pump.
As the engine warms up the thermostat begins to open (A2) and some of the coolant flows to the top of the
radiator.
The thermostat will open fully (A3) when the engine reaches the normal temperature of operation. When the
thermostat is open (A3), the by-pass valve is closed and the coolant passes to the top of the radiator.
The thermostat maintains the correct engine temperature by a balance of by-pass flow and full flow to the top
of the radiator.
Air passes over the radiator fins and heat is removed from the coolant as it passes through the radiator. The
coolant leaves the radiator through the bottom hose and returns to the coolant pump.
Workshop Manual, TPD 1345E, issue 3 195
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