When a clutch fan fails it causes the coolant to retain heat, forcing the engine to run hot and eventually overheat. A clutch fan is engaged and disengaged from operation by the heat produced from the radiator.

This fan clutch is constructed using a silicon grease and temperature sensitive coil spring that expands and contracts with heat. As the spring absorbs heat it expands engaging the clutch utilizing engine power to drive the fan. As the engine coolant cools the fan clutch will disengage.

A clutch fan can fail one of two ways, it can either lock the fan to the clutch causing poor mileage and a whirring sound, like an airplane is taking off next to you. Or the silicon grease can start to leak causing the fan clutch not to lock up allowing the fan to "freewheel", failing to pull air through the radiator when needed.  When the clutch fails, there are no repairable parts inside. It is easier to simply replace the entire unit.


 

 DISASSEMBLY

 233

Tools required for repair

222

Fan and clutch assembly prior to removal.

223

There is no need to remove any belts or other components to facilitate removal of the fan and clutch assembly.

224

Four nuts and their lock washers that secure the assembly to the water pump need to be removed.

225

Carefully remove the fan assembly.

226

Four remaining studs after removal of the assembly.

227

The assembly after removal. The collar should spin freely.  If it doesn't then the fan will turn constantly and the clutch needs to be replaced.

229

The red arrow indicates leakage of fluid from the clutch.  Watch for these type of marks when trouble shooting.

230 

Remove four bolts and separate the fan from the clutch.

231

 Bolts removed - the fan can now be removed from the clutch.

232 

Two separate units.

234

 Leaking clutch.  This particular unit was replaced with a new clutch from Parts Source - their part number 2714. 


 

Reassembly

clutch_fan

Principal Behind Clutch Fan Operation

The fan clutch has a fluid coupling partly filled with silicone oil designed for just that purpose. When the temperature of the air passing through the radiator rises, the heat alerts a bimetal coil spring to "uncoil" or expand. When it expands, it allows just a little more oil to enter the fluid coupling, so the fluid coupling starts to rotate the fan. If the air coming through the radiator is cool, the opposite happens; the coil spring contracts, the oil leaves the fluid coupling and the fan slows. Slowing the fan when it is not needed reduces fuel consumption, makes less noise and saves engine power. Sometimes a flat bimetal strip spring is used instead of a coil spring; it bows out and in when the temperature rises and drops, letting oil in and out of the fluid coupling.


 

Notes:

Noise 

Fan noise is sometimes evident under the following conditions:

When clutch is engaged for maximum cooling.

During first few minutes after start-up until the clutch can re-distribute the silicone fluid back to its normal disengaged operating condition after overnight settling.

Fan noise or an excessive roar will generally occur continuously, however, under all high engine speed conditions (2500 r.p.m. and up) if the clutch assembly is locked up due to an internal failure.  If the fan cannot be rotated by hand or there is a rough grating feel as the fan is turned, the clutch should be replaced.

 

Looseness

Under various temperature conditions, there is a visible lateral movement that can be observed at the tip of the fan blade.  This is a normal condition due to the type of bearing used.  Approximately 1/4"(6.5mm) maximum lateral movement measured at the fan tip is allowed.  This is not cause for replacement.

 

Silicone Fluid Leak

The operation of the unit is generally not affected by small fluid leaks which may occur in the area around the bearing assembly. 

 

Engine Overheating

If the fan and clutch assembly free-wheels with no drag (revolves over 5 times when spun by hand), the clutch should be replaced.

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