# Faulty Fan Clutch ???



## student (Mar 31, 2004)

I am having over heating problems and have replaced everything related to cooling in the past 3k miles. Just recently my car begain overheating again and i had orginally thought it was the thermostat, so i replaced it again. The mechanic then noticed that the fan was not engaging all the time, so i took it back to the original mech and they agreed it may be faulty and then replaced it free (hayden brand). Made it 10 mins bagain overheating, popped hood and fan once again is not engaged (free spinning w/ motor). Mech said that maybe he has a bad lot of fan clutches, gave me my money back for the part and told me to go and buy one @ NAPA. Same thing, hot car and fan clutch is not engaging. Turn car off wait a few mins, start car, up, clutch engages and works for a few mins then disengages. 

PS. Dont think this has anything to do with it, but my alternator is on the fritz. Batt light is on along w/ others when i accelerate, lights are dim when idle. 
What in the world would cause this, I'm stumped and so is my "mechanic".

Please help, thank you


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## Zen31ZR (Mar 24, 2004)

The fan is not supposed to be engaged all the time. The clutch inside those is awash in a temperature sensitive silicone gel , when it hot gets due to hot radiator air blowing on it the silicone gel "locks" up and makes the fan spin. If its not locking up and spinning even thought the motor gets hot , I'd take that to mean the radiator may be at fault. If the radiator were more accessable , I'd say put your hand on it (be careful) in various places , and if you feel any cold spots that indicates a blockage. If the inlet side is hot , but the outlet side is cold , that indicates a major blockage. 
Since you've replaced all the other components generally known to go wrong , I'd be suspecting the radiator.


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## JAMESZ (Mar 12, 2004)

What model Z is this? Before the Z32 all of the clutch fans ran straight off the belt and stayed at the pulleys angular velocity. I won't get into the trig but it should be at the same angular velocity as the pulley and should never change on anything older then the Z32. Also what temp is it reading at when you overheat?


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## Zen31ZR (Mar 24, 2004)

JAMESZ said:


> What model Z is this? Before the Z32 all of the clutch fans ran straight off the belt and stayed at the pulleys angular velocity. I won't get into the trig but it should be at the same angular velocity as the pulley and should never change on anything older then the Z32.



They tend to , yes , but they coast a bit and generally lag behind the pulley in overall rpms , especially during acceleration. But after the silicone heats up , it's definitely a 1:1 ratio , or at least it should be. I'd say it's a statistical impossibility for him to have gotten 2 bad fan clutches in a row , so something else must be wrong here.


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## 300jet (Mar 31, 2004)

The fan will rotate at different velocities at different engine revs according to the temperature of the clutch fan unit ... or at least it should.

When they get old and start to malfunction, they tend to stick on, or become almost direct drive at all temperatures (which makes an obvious fanny type sound). 

For x amount of time the fan will also lock on after starting your car, but it will slacken off in something like 10 seconds. It's normal on all the clutchies i've had, probably something to do with the mysterious way they work.(a liquid or gel that gets thicker with heat??)

so it looks like it's not your fan. maybe blocked radiator, and if no rad coolant was run in the motor, then maybe water pump. Also if it is only getting to just over half way up the heat gauge, then stopping, something else is to blame


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## JAMESZ (Mar 12, 2004)

umm if this is a Z31 it stays with the pulley. My 86 T had the original clutch fan in it back in the day and their is only a spring in it. In the Z31 it is always running.


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## Zen31ZR (Mar 24, 2004)

JAMESZ said:


> umm if this is a Z31 it stays with the pulley. My 86 T had the original clutch fan in it back in the day and their is only a spring in it. In the Z31 it is always running.


I think JDM is different. US spec fan clutches since the 70s have heat sensitive silicone fluid in them. Its just like a viscuous LSD differential.
If they get very old , or leak out all the silicone fluid , after a while they barely idle at 1/2 pulley speed , and lag FAR behind during acceleration. Some seriously bad ones I've come across , you can actually grab the fan and stop it while the engine is running. If the clutch was good , there's no way you would be able to do that.

A good fan clutch test is to try to spin it while the engine is warm and off. You shouldn't get more than 1 or 2 rotations out of it. A bad fan clutch will spin quite a few times.


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## JAMESZ (Mar 12, 2004)

Humm that might be it. I gotta love JDM hehe. It is just confusing as hell when some things that should be on the car (usdm manuals don't have everything) aren't there. I spent a freakin hour looking for a temperature sensor that is on the USDM engine but apparently not on my JDM  . But I highly doubt they would change something like that between the USDM and JDM. I know they have something like you speak of in the Z32 but in the Z31 I still am not sure.


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## Zen31ZR (Mar 24, 2004)

JAMESZ said:


> Humm that might be it. I gotta love JDM hehe. It is just confusing as hell when some things that should be on the car (usdm manuals don't have everything) aren't there. I spent a freakin hour looking for a temperature sensor that is on the USDM engine but apparently not on my JDM  . But I highly doubt they would change something like that between the USDM and JDM. I know they have something like you speak of in the Z32 but in the Z31 I still am not sure.


Its the type of fan clutch that's on my car , and if it's aftermarket it may be different in function but not in intended result. The spring thingy you are talking about is mounted on the front of a typical fan clutch , and has something to do with heat transfer , in any case I know it's thermal reactive.

That missing sensor you are talking about I think is the head temperature sensor. It has something to do with emissions here , and I know JDM wasn't too concerned with emissions , and had different ways of dealing with emissions problems.


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## JAMESZ (Mar 12, 2004)

Humm maybe. But I am loving my electric fan conversion  . Wow I didn't think it would make such a big difference in power. Once I am up in the higher rpms it pulls harder then before. And cooling efficiency is up hehe.


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## Zen31ZR (Mar 24, 2004)

JAMESZ said:


> Humm maybe. But I am loving my electric fan conversion  . Wow I didn't think it would make such a big difference in power. Once I am up in the higher rpms it pulls harder then before. And cooling efficiency is up hehe.


Yeah , that's my next trick. I'm having hot start problems now. Not overheating yet , but I'm pretty sure my fan clutch is on the way out too.


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## JAMESZ (Mar 12, 2004)

Hehe mine wasn't dying the car ran perfectly fine before and it just runs better now :cheers: . Hehe Next thing to do humm I dunno. I am going to install my limited slip because dang no traction sucks arse. I want good traction before 60 (before I get ready to shift to 3rd gear)  . Hopefully my LSD will help fix this and Ill go the next level up in the Potenza realm and get S-03 Pole Positions.


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## 0341TODD (Nov 15, 2003)

At normal temp. where does your guys temp guages sit? I just put a 170 thermostat in my car and switched my electric fan so its always on- I think Im going to change my fan clutch too- the summers down here are killer on cars and I dont want to get stuck somewhere! My gauge usually sits right under the middle- more to the left- does that sound about right? Obviously location and sea level will come into play with the answer, but are you guys just about the same?


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