5.2.1 Thermostat
DETROIT DIESEL 53
2. Remove the hose connections between the thermostat housing water outlet elbow and the radiator or heat
exchanger.
3. Loosen the bolts and remove the water outlet elbow from the thermostat housing on the in-line engine (Fig. 2).
Take out the thermostat.
Inspection
If the action of the thermostat has become impaired due to accumulated rust and corrosion from the engine coolant so
that it remains closed. or only partially open, thereby restricting the flow of water, overheating of the engine will result. A
thermostat which is stuck in a wide open position may not permit the engine to reach its normal operating temperature.
The incomplete combustion of fuel due to cold operation will result in a build-up of carbon deposits on the pistons. rings
and valves.
The operation of the thermostat may be checked by immersing it in a container of hot water (Fig. 4). Place a
thermometer in the container, but do not allow it to touch the bottom. Agitate the water to maintain an even temperature
throughout the container. As the water is heated, the thermostat valve should begin to open when the temperature
reaches 167 - 172F. (In-line engine) or 174 - 176F. (V-engine). The opening temperature is usually stamped on the
thermostat. The thermostat should be fully open at approximately 190- 192F.
Clean the thermostat seating surface in the thermostat housing and base or the water outlet elbow.
Check the bleed hole in the thermostat housing to be sure it is open (Fig. 5).
Drill a 3/32" diameter hole in the thermostat housing used on in-line industrial engines built prior to serial number 3D-011
(refer to Fig. 6). This will provide a coolant drain hole for the by-pass cavity in the housing.
Install Thermostat
Refer to Fig. 2. and install the thermostat(s) as follows:
IN-LINE ENGINE:
1.
Place a new gasket on the thermostat housing.
Fig. 4. Method of Checking Thermostat Operation
Page 2
