Perkins 900 Series Workshop Manual page 207

12
900 Series
Thermostat
The thermostat is held in a sealed brass or sealed plastic housing, and held in position by three hoses: the top
radiator inlet hose, the by-pass hose to the coolant pump and the outlet hose from the cylinder head. The
thermostat housing can be fitted in the horizontal position (A) or the vertical position (B) in accordance with the
engine application.
If the thermostat does not operate correctly the complete assembly must be renewed.
To remove and to fit Operation 12-1
To remove
1 Drain the cooling system until the coolant level is below the thermostat position.
2 Release the clips of the three thermostat hose connections. Remove the thermostat unit from the hoses.
To fit
1 Ensure that the hose connections are clean and that the jiggle pin fitted inside the thermostat valve is free
to move.
Caution: The flange (A2) or (B1) on the brass thermostat housing must be toward the radiator connection
when the thermostat is fitted. If the assembly is fitted incorrectly, the engine will overheat as the flow of coolant
will not pass through the radiator.
2 Put the new brass thermostat into position on the three hoses, if the brass thermostat is fitted horizontally
(A), ensure that the vent screw (A1) is at the top. If the thermostat is fitted in the vertical position (B), ensure
that the flange on the thermostat body is at the top (B1) and is connected to the radiator hose.
Caution: If the brass thermostat is fitted horizontally, it is important to eliminate air from the cooling system
when it is filled. Ensure that the vent screw (A1) is released until it tightens. When coolant, free from air flows
from the vent point, tighten the vent screw to 3-4 Nm (2-3 lb ft).
3 If a plastic thermostat is fitted, connect the radiator, engine and the pump hoses to the correct outlets,
identified by the arrows on the thermostat body
Note: if a plastic thermostat is fitted, it is not necessary to eliminate air from the thermostat housing as no vent
screws are fitted
4 Tighten the three hose clips.
5 Fill the cooling system, see Operation 12-3
1
1
2
A B
C0008
C0096
Workshop Manual, TPD 1345E, issue 3 197
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