Fan Clutch Replacement
The clutch fan is a very nice invention compared to a non clutch type fan. A clutch type fan allows the fan to freewheel when the tempature of the motor is low and then spin when tempatures reach a set point. Most of the time it wotks well. When it fails the symptoms may vary from overheating only at idle or highway speeds to excessive fan noise. It can also destroy a perfectly good water pump.
Symptoms can vary widely. If the clutch has lost fluid it may slip excessively. It may allow overheating at low rpms but allow adequate cooling at highway speeds. It may do just the opposite. Or allow over heating under any driving condition. Parts inside may come into contact and lock the fan after heating up and over spin the fan generating excess noise. Some things to check are as follows:
- Look for oil on the outside of the clutch body
- Grab the fan (with the engine off!) and move it side to side while looking for excessive Play
- Rotate the fan by hand. It should turn free. Try to give it a good spin. If it rotates more than half a turn it may have lost fluid
If you have an overheat problem that defies diagnosis, it may be the thermostatic clutch. Something else to think about. The clutch is “stack mounted" on the water pump. If the clutch is bad, and out of balance, it can and often will cause failure of the water pump bearings. Considering the clutch is often between $30 and $60, and you have a mysterious overheat problem, it is worth the price to replace.
Replacing The Clutch
Replacing the Fan Clutch is not all that hard. Remove the plastic cowling from around the fan. There is the one bracket on top and several metal clips securing the bottom. Hang on to the clips. You'll have to Wiggle the cowl around to get it off and around the fan. Next remove the four 10mm nuts holding the clutch in place. (see image top) Be careful not to remove the pulley. The pulley is held on by the same nuts. If the pulley Comes off you will need to loosen the fan belt to get it back together. Once the clutch is off reverse the order of disassembly to install the new one. Put this metal clips back on the bottom. The top edge of the cowling hooks onto a groove on top.
Sources Used on This Page: 1984-1988 Nissan 300ZX Factory Service Manual