Cooling Fan Clutch

[jadahl25]

I'm a newbie in need of help.

91 300ZX TT

Managed to work through replacement of the cooling water pump. On restart, but continuing into driving, there was a considerable amount of noise from, I am almost certain, the cooling fan. So I replaced the cooling fan thermal clutch with an after market. Clutch only, not the fan head.

Still have the noise and it really bugs me. I thought that a thermal clutch would let the fan freewheel until the engine warmed up and then engage the blades. Obviously not happening.

And, most peculiar to me. The car has installed electrical components identified with the radiator fan; a radiator fan relay and sub relay. And discussed in the 91 Shop Manual with a trouble shooting section and wiring diagrams.

Any help will be appreciated.

I do not know the protocol on this site. If it is allowed to reply directly, my email is [email protected]

Thanks,

Joe

[t.mcginley.jr]

What does the noise sound like? if you could take a video and post it on YouTube it would help diagnose it easier, sounds are hard to describe in words.

What brand of water pump did you use?

[jadahl25]

Hi,

Thanks for the reply. I don't think you would see anything in a video or even a still photo. The noise is definitely from the fan which does not have any cracks or cuts that would account for the noise. After replacing the water pump, to check for leaks, I ran the car before attaching the clutch and fan. No noise then.

Have you any thoughts about whether the thermal clutch should disengage when the engine is cool (after running for a few seconds)?

Or why the car has a radiator fan relay and sub relay? That are shown and discussed in the shop manual? The obvious guess is that the car originally had an electric fan which was replaced by a previous owner. I bought the car used and never thought about that until now.

At any rate, thanks.

Joe

[t.mcginley.jr]

The radiator fan relay and sub relay is just for the accessory fan that's in front of the radiator. It's actually for the AC condensor but aftermarket repair manuals aren't always 100% accurate. It only kicks on in certain conditions. All 300zx's came with clutch fans, no electric ones.

The clutch should only be moving at full speed when the engine is warm. When it's cold it should be slower. Many people have had problems with aftermarket (parts store) fan clutches being bad right out of the box. How hard is it to spin by hand?

[jadahl25]

Now we know why I need (and appreciate) help. I did not know that there was a fan in front of the radiator. I have an 88 Acura Legend coupe and it has two electric fans but they are visible immediately on the engine side of the radiator.

The shop book I have is a Nissan Shop Manual, but it says almost nothing about the cooling fan clutch. Now I know.

As to the generic one I bought from Advance Auto, out of the box it was pretty much as difficult to spin by hand as the one I took off, which may or may not have been OEM. Starting the engine cold, the fan seems to spin at speed and not slow down even for a short time. Can't tell if it is spins faster when the engine is at temperature.

I truly appreciate your interest and assistance.

Joe

P.S. If I can add another question that I can't find answered in the manual. There are two cables coming out from under the cover between the turbos. Both ride on a sprocket. The one on the driver's side, when rotated by hand, rotates a shaft between the two intakes. There is on this shaft an adjusting screw similar to what used to be found on cars and used to set the idle. I know this is not the case on the ZX, but what is that adjustment for and where should it be.

[t.mcginley.jr]

Usually when the clutch is bad, it either free-wheels too much or its stuck and moves an excessive amount of air even at idle. I've never heard of a bad one making noise though. Are you sure everything is tightened down good? Is the belt too tight or too loose?

As for your other question, are you talking about these cables?



If so, the cable closest to the drivers side is the accelerator cable. It's connected directly to your gas pedal and opens the throttle bodies on the intake to let more air in. The other cable is for cruise control, it basically does the same thing except its controlled by the computer.

[jadahl25]

Thank you for the response.

In the case of noise I don't think it is the clutch, I do think it is probably noise from the fan which I hear because the clutch is turning too fast. Especially at low speeds. The sound I get seems to be similar to that from a floor fan when I turn it up from low to high.

So maybe the real question is how to tell whether the thermal clutch is working okay or is defective. Off the car and turning it by hand there is significant resistance, it certainly doesn't free wheel. What comes to mind is pushing something through peanut butter or 140 w oil.

Without really knowing, I would have thought that it would free wheel until heat from the radiator acted on the clutch expansion spring or whatever the thing is called.

As to the cables, yes the ones I was referring to are shown in your photo except my model has an adjusting screw on the accelerator cable. Is that supposed to be set so as to take out any slack in the cable??

Again, thank you

Joe

[DCaff300ZX]

Your clutch fan should spin very freely by hand on or off the car, and indeed should begin to get "stiffer" as it warms up with the engine and the friction of being moved. Bad ones will have the fluid inside become too gummy or even begin leaking out, causing the unit to seize and produce the loud wind noise you are hearing.
Every Z person I have talked to about this issue, which I had years ago after a t-belt job at a shop that had no business doing it, has said to go with ONLY an OEM clutch fan for the Z32 whether new or used, as the aftermarket ones have a very high fail rate.

Not sure about the screw you mentioned as I have nothing different in my '93 TT than the pic above, which shows how to adjust your throttle cable for slack- dialing in or out the hollow threaded part the wrench is on after loosening the locking nut on the front.

[jadahl25]

Thank you. The clutch observation makes sense. I first encountered the noise after reinstalling the clutch and fan after replacing the cooling water pump. I bought a replacement from the auto parts store (Advance). I noticed that it was stiff to turn as was the original pump I took off. The auto parts person checked a couple of other thermals they had on the shelf and they told me those were all stiff. So I did a little research on line and came across an article (don't remember where, but not on this forum) which said it would be stiff until it ran a bit and pumped the fluid back into the storage reservoir. I foolishly accepted this until I started quizzing on this forum and you were kind enough to help.

It happens that earlier today I ordered another replacement through the parts store, but from factory that makes thermal clutches. Twice the price of the first one. And I removed the fan, started the car, loud noise. Took off the fan clutch and pulley, started the car, no noise. Confirms that the noise I was hearing was fan noise from the blades running at peak speed. Now I await the replacement.

re the screw. My 91 has a fixture on the accelerator shaft with an adjusting screw that acts on a fixed plate. Turning it does the same thing as turning the nuts in the photo Mr. McGinley attached to his reply.

Thank you for taking the time.

Old Dog Learning New Tricks