5.2.1
DETROIT DIESEL 53
THERMOSTAT
The temperature of the In-line engine coolant is
controlled by a single choke type thermostat located in
a housing attached to the water outlet end of the
cylinder head.
On the In-line
engines, a by-pass tube is attached between the
thermostat housing and the water pump.
At coolant temperatures below approximately 170"F.,
the thermostat valve remains closed and blocks the
flow of coolant through the radiator or heat exchanger.
During this period. the coolant circulates through the
cylinder block and head and then back to the suction
side of the pump via the by-pass tube. As the coolant
A properly operating thermostat is essential for
temperature rises, the thermostat valve begins to open,
efficient operation of the engine. If the engine
restricting the by-pass system and permits the coolant
operating temperature deviates from the normal range
to circulate through the radiator or heat exchanger
of 160F - 185F., remove and check the thermostat(s).
With the valve fully opened in the in-line engine, a
Remove Thermostat
very small portion of the coolant will continue to
1. Drain the cooling system to the necessary level by
circulate through the by-pass tube, while the major
opening the drain valves.
portion will pass through the radiator.
Fig. 2 Thermostat Housing Details and Relative Location of Parts (In-Line Engine)
July, 1971 SEC. 5.2.1 Page 1
