DESCRIPTION & OPERATION
| WARNING | Vehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article. |
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery. |
VISCOUS FAN DRIVE
| CAUTION | If viscous fan drive is replaced because of mechanical damage, cooling fan blades should also be inspected. Inspect for fatigue cracks, loose blades or loose rivets that could have resulted from excessive vibration. Replace fan blade assembly if any of these conditions are found. Also inspect water pump bearing and shaft assembly for any related damage due to a viscous drive malfunction. |
The thermal viscous fan drive consists of the viscous fan drive clutch and a thermostatic spring coil mounted on its front face. The viscous fan drive clutch is s silicone-fluid-filled coupling connecting fan blade assembly to water pump shaft. The coupling allows fan to be driven in a normal manner at low engine speeds. It will limit top speed of fan to a predetermined maximum level at higher engine speeds. The thermostatic spring coil reacts to the temperature of radiator discharge air. It engages drive clutch for higher fan speed if air temperature from radiator rises above a certain point. Until additional engine cooling is necessary, fan will remain at a reduced RPM regardless of engine speed. Only when a sufficient heat is present in the air, will the viscous fan drive clutch engage. This air flowing through radiator core will cause a reaction to thermostatic spring coil. Fan speed will then increase to provide necessary additional engine cooling.
Regardless of increased engine speed, once the fan reached its maximum operating speed, it will not rotate any faster. When the necessary engine cooling has been accomplished causing a reduction in temperature of radiator discharge air, the spring coil again reacts. This will cause fan speed to be reduced to its previous disengaged speed.
REMOVAL & INSTALLATION
| WARNING | Vehicles are equipped with air bag supplemental restraint system. Before attempting any repairs involving steering column, instrument panel or related components, see SERVICE PRECAUTIONS and DISABLING & ACTIVATING AIR BAG SYSTEM in appropriate AIR BAG RESTRAINT SYSTEMS article. |
| CAUTION | When battery is disconnected, vehicle computer and memory systems may lose memory data. Driveability problems may exist until computer systems have completed a relearn cycle. See COMPUTER RELEARN PROCEDURES article in GENERAL INFORMATION before disconnecting battery. |
Note. For more information, refer to VISCOUS FAN DRIVE .
Fan belt is not necessary to remove cooling system fan.
- Disconnect the negative battery cable at battery.
- Remove the plastic air cleaner intake tube.
- Remove two-piece fan shroud. (Scheme 1) Remove lower half first.
- The thermal viscous fan drive/fan blade assembly is attached (threaded) to the water pump hub shaft. (Scheme 2) Remove the fan blade/fan drive assembly from water pump by turning the mounting nut counterclockwise (as viewed from front). Threads on the viscous fan drive are RIGHT HAND. A Snap-On 36 MM Fan Wrench (number SP346 from Snap-On Cummins Diesel Tool Set number 2017DSP) can be used. Place a bar or screwdriver between the water pump pulley bolts to prevent the pulley from rotating. (Scheme 2)
- After removing fan blade/fan drive assembly, do not place the thermal viscous fan drive in the horizontal position. If stored horizontally, the silicone fluid in the viscous fan drive could drain into its bearing assembly and contaminate the bearing lubricant.
- Remove the 4 bolts securing the fan blade assembly to the viscous fan drive.
- To install, reverse removal procedures. Tighten bolts to 23 N.m (17 ft. lbs.).
Scheme 1
Scheme 2
See COOLING SYSTEM FAN for removal and installation procedures of the viscous drive unit.
Viscous Fan Drive Fluid Pump Out Requirement - After installing a new viscous fan drive, bring the engine speed up to approximately 2000 RPM and hold for approximately 2 minutes. This will ensure proper fluid distribution within the drive.
TORQUE SPECIFICATIONS
| Application | Ft Lbs. (N.m) |
|---|---|
| Fan Blade Assembly Bolt | 17 (23) |
TORQUE SPECIFICATIONS
See also:
• VISCOUS FAN DRIVE
• COOLING SYSTEM FAN