Seal failure is readily noticed by a flow of water visible
Miscellaneous Cooling System Checks
at the openings in the raw water pump housing, located
between the pump mounting flange and the inlet and
In addition to the above cleaning procedures, the other
outlet ports. These openings must remain open at all
components of the cooling system should be checked
periodically to keep the engine operating at peak
efficiency. The thermostat and the radiator pressure
cap should be checked and replaced, if found defective.
The cooling system hoses should be inspected and any
hose that feels abnormally hard or soft should be
Also, check the hose clamps to make sure they are
tight. All external leaks should be corrected as soon as
detected. The fan belt must be adjusted to provide the
proper tension, and the fan shroud must be tight against
the radiator core to prevent recirculation of air which
may lower cooling efficiency.
Fresh Water Pump
A centrifugal-type fresh water pump is mounted on top
Fig. 19. Raw Water Pump Used on In-Line Engine
of the engine oil cooler housing, either on the right-hand
or left-hand side of the engine, depending upon the,
The impeller, cam and wear plate assembly, and water
engine model and rotation. It circulates the coolant
seal assembly may be serviced without removing the
through the cooling system.
pump from the engine as outlined below.
The pump is belt driven, by either the camshaft or
1. Remove the cover and gasket.
balance shaft (In-line engines) or by one of the
2. Note the position of the impeller blades to aid in the
camshafts (V-type engines).
reassembly. Then grasp a blade on each side of the
impeller with pliers and pull the impeller off of the shaft.
An impeller is pressed onto one end of the water pump
3. The neoprene spline seal(s) can be removed from
shaft, and a water pump drive pulley is pressed onto the
the impeller by pushing a screw driver through the
opposite end. The pump shaft is supported on a sealed
impeller from the open end.
double-row combination radial and thrust ball bearing.
Coolant is prevented from creeping along the shaft
toward the bearing by a seal. The shaft and bearing
constitute an assembly and are serviced as such, since
the shaft serves as the inner race of the ball bearing.
The sealed water pump shaft ball bearing is filled with
lubricant when assembled. No further lubrication is
Contact an authorized Detroit Diesel Allison Service
Outlet if more information is needed.
Raw Water Pump
The raw water pump (Figs. 19 and 20) is a positive
displacement pump, used for circulating raw water
Fig. 20. Raw Water Pump Used on V-Type Engine
through the heat exchanger to lower the temperature of
the engine coolant. It is driven by a coupling from the
end of the camshaft.