Detroit Diesel 4000 Series, Service Manual, Page: 1756 / 2706

SERIES 4000 12/16V SERVICE MANUAL
Oil then travels through the orifice, through the bracket, and into the fan clutch shaft. Oil passages
in the shaft distribute lubricating oil to the bearings and other internal parts, and into the clutch hub
cavity. Centrifugal force drives oil through slots in the clutch hub to cool the clutch plates. The
grooved configuration of the facing plates allows oil to pass over the clutch plates at all times. It is
this flow of cooling oil over the clutch plates which permits clutch slip and variable fan speeds.
NOTICE:
The pitot tubes pump oil from the pulley and maintain low internal
pressure in the fan clutch. Never run the engine without belts
driving the fan clutch pulley.
Centrifugal force carries the oil outward to the inside diameter of the pulley (or pulley adapter).
The rotational movement of the pulley carries the oil in the direction of input rotation. Pitot tubes
face into the direction of input rotation. The rotational movement of the oil rams the oil into the
pitot tubes, which direct the oil through a passage into and through the fan clutch shaft and bracket,
to an external "OIL OUT" port. A line from the "OIL OUT" port carries the oil to an unrestricted,
non-pressurized port on the engine where the engine oil is returned to the engine oil sump.
Control Pressure Oil
The Rockford fan clutch is controlled by oil pressure supplied through the solenoid valve. Engine
oil flowing from the "COM" or "CLUTCH" port of the solenoid valve enters the fan clutch
through the "CONTROL PRESSURE" port of the shaft and bracket assembly and travels through
shaft to the control pressure cavity of the fan clutch, which is formed by the piston and the pulley
(or pulley adapter). Pressure reacting within the pressure cavity, forces the piston against the
clutch plates to create a drive through the fan clutch. As the engine cools, oil in the pressure
cavity exhausts back through the same oil line attached to the "COM" or "CLUTCH" port of the
solenoid valve and is dumped by the solenoid back to the engine oil sump through the "NC" or
"SUMP" port in the solenoid valve.
Rockford Part Numbering System
Rockford Fan Clutch part numbers have changed in the way they were displayed in print over the
years, primarily due to advances in technology.
The part number format for a Rockford Fan Clutch Assembly is 040XXXX, where XXXXX is
a five digit alpha number unique to that particular assembly.
Pervious numbers may have been displayed as: 4-XXXXX, 40XXXXX, 04-XXXXX, or
4-0XXXXX. The unique five-digit number remains unchanged, regardless of how the prefix
may have been written at one time or another.
A serial number is assigned to each fan clutch produced by Rockford Powertrain, Inc.
Fan Clutch Part Number and Serial Number
Refer to the nameplate for part number and serial number information.
All information subject to change without notice.
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