My Datsun hasn't been staying cool enough lately so the other night I decided to "rebuild" the fan clutch. It was a really easy job and took no more than 45 minutes. The car has been running really cool since! Here's a short guide on what I did.
Step 1: Remove the fan and clutch from the water pump pulley. It's attached with four 10mm nuts.
Step 2: Remove the fan from the clutch via the four nuts/bolt I've circled below.
Step 3: Separate the fan from the clutch and flip her over. You will see the thermostat spring on the front of the clutch that acts to "tell" the clutch how much or little to slip depending on the temperature of the engine. To take the clutch apart, remove the four phillips head bolts that I've circled in red.
Step 4: Separate the two halves of the clutch with a utility knife or flathead screwdriver. They should come apart pretty easily.
The inside of the clutch is filled with an extremely thick silicone based lubricant. This stuff was far too old and viscous to allow my cooling fan clutch to slip at the right speed. This junk is what was causing my Z to run a little too warm.
Step 5: Clean both halves of the clutch with brake cleaner. Start by spraying off excess gunk, put the clutch on flat surface, spray again and let the brake cleaner sit and penetrate all the way in the clutch.
Step 5.5: Use three cans of brake cleaner because this stuff is so thick.
Step 6: Refill inside of clutch with new lubricant. I chose to use Pennzoil 80W-90 Gear Lubricant. This stuff is thick as molasses, but less viscous than what was previously in the clutch.
Lay both halves flat, slowly refill them and allow the lubricant to sink all the way in.
After both halves have been refilled, put the two together and reattach everything. Reattach the fan clutch to the water pump pulley, then start your car up to make sure it all works. Go for a test drive and you car should be running cooler!