Miscellaneous Cooling System Checks
In addition to the above cleaning procedures, the other
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 replaced immediately.
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 re-circulation of
air which may lower cooling efficiency.
Fig. 20 - Raw Water Pump Used on In-Line
inlet and outlet ports. These openings must remain
A centrifugal-type water pump is mounted on top of
open at all times.
the engine oil cooler housing, either on the right-hand
or left-hand side of the engine, depending upon the
engine model and rotation. It circulates the coolant
The impeller, cam and wear plate assembly, and water
through the cooling system.
seal assembly may be serviced without removing the
pump from the engine as outlined below.
The pump is belt driven, by either the camshaft or
balance shaft (In-line engines) or by one of the
1. Remove the cover and gasket.
camshafts (V-type engines).
An impeller is pressed onto one end of the water
2. Note the position of the impeller blades to aid in
the reassembly. Then grasp a blade on each side of the
pump shaft, and a water pump drive pulley is pressed
onto the opposite end. The pump shaft is supported on
impeller with pliers and pull the impeller off of the
a sealed 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
3. The neoprene spline seal(s) can be removed from
bearing constitute an assembly and are serviced as
the impeller by pushing a screw driver through the
such, since the shaft serves as the inner race of the ball
impeller from the open end.
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. 20 and 21) is a positive
displacement pump, used for circulating raw water
through the heat exchanger to lower the temperature
of the engine coolant. It is driven by a coupling from
the end of the camshaft.
Seal failure is readily noticed by a flow of water
Fig. 21 - Raw Water Pump Used on V-Type
visible at the openings in the raw water pump housing,
located between the pump mounting flange and the