MAINTENANCE OF THE M88A1 - OD1672 - LESSON 2/TASK 1
When the engine is operating, the fans draw air through the cylinder fins
and oil coolers and discharge hot air vertically from the shroud.
cooling fans are attached to hubs and are mounted on shafts driven by a
horizontal drive shaft clutch assembly. The fan drive shaft and gear shaft
are driven by a horizontal drive shaft.
The hub and fan assemblies are
balanced, but an assembly can be replaced without affecting the balance of
the complete unit. However, the hub and fan on an assembly should not be
separated, as this could affect the balance of that assembly as a unit. The
two fan and hub assemblies are interchangeable.
(4) Fan Clutch. The fan clutch is oil cooled. The fan clutch drive
and driven disks are loaded by the centrifugal action of clutch balls and
springs housed in the clutch assembly.
The balls and springs are in the
driven member and apply upward force to the clutch disks. The clutch oil
enters the fan drive vertical shaft from the fan drive housing through an
annular groove in the shaft. The depth of the groove controls the amount of
The oil flows through a central hole in the shaft to a distributor where it
is dispersed to the two ball bearings and to the clutch disks by centrifugal
The oil then drains back through the fan drive housing into the
engine oil pan. The fan clutch is designed to slip under deep water fording
conditions where the resistance of the water exceeds the friction of the
(5) Oil Coolers. A total of two engine and two transmission radiator-
type oil coolers (figure 11, view B, on the previous page and figure 12,
view A, on the following page) are required for cooling the engine and
transmission oil. One engine and one transmission oil cooler are mounted on
a frame (figure 12, view B) on each side of the engine above the cylinders.
Air is drawn through the oil cooler cores to cool the oil circulated within
the coolers from the engine and transmission.
(6) Engine Oil Cooler Lines and Connections. Separate oil inlet and oil
outlet cooler lines (figure 13, views A and B, on page 33) connect the
engine and the transmission to their separate oil coolers.