Thermal Fan Clutch? (Video)

I replaced all of the cooling components last year on my 97 XJ 4.0L and even installed a good three row radiator. The XJ is now running between the 210 mark and the next one. It began to act this way after it overheated while pulling a trailer this spring, before that it ran exactly at or just below 210. Anyway, I have put a Prestone flush chem inside and have been running that as I saw the water looked rusty and had sediment in the bottom of the reservoir bottle. I also put in a NAPA 180* thermostat (just for $%^ and giggles)which seemed to do nothing as the temp is still above 210. I took a video of me turning the mechanical fan by hand right after I turned the XJ off and popped the hood. It seemed to spin pretty freely. I could spin and let go and it would make one half revolution. Is that right? Need a new one already after I replaced it last year? Seemed to get warm when driving and at idle.

Here is a link to the video:

http://s167.photobucket.com/albums/u152/mmantzouranis/JEEP/?action=view&current=Picture053.flv

Let me know if the link does not work.

Seems pretty loose.

Might be out.

That's the way mine spins when it's cold. If the engine was warm, that's all wrong.

Yeah the engine was above 210 when i shut it off so I was expecting the fan to be tight. How tight is your fan when it is at 210?

Mikey said:

Yeah the engine was above 210 when i shut it off so I was expecting the fan to be tight. How tight is your fan when it is at 210?

Click to expand...

My 94 spins feely and is shot. My 96 is tight as a drum when hot.

I obviously am going to replace the fan clutch. Is there any brand or style fan clutch out there that is better than the rest? What is a non-thermal fanclutch? I had also seen one that says it is heavy duty that autozone offered, but what does it mean by heavy duty?

Thermal fan clutch uses a silicone based fluid and a temperature sensitive spring to "stiffen" the clutch when warm so the fan spins faster.

Non-thermal or Centrifugal fan clutches use the same type design, only no thermostat spring, they simply turn at a specifc rate of speed per given engine RPM. Atleast this is how it was explained to me.....

If you need a heavier duty fan, go centrifugal, as it pulls more air at low RPM. You will lose a little mileage, but it may help it stay cooler.

you found your gremlin....that fan clutch is shot to hell,replace it and your temps should go down.
Another thing you could do if you don't have the $$ to get the clutch right now is use bolts to lock the clutch in place(do a search for this)

My brand new clutch has the thermal spring, but I cant notice it spinning any faster when the engine is hotter, but I absolutely notice it when the RPMs are up. If I notice the temp going up at a stop light, I pop it in neutral and rev at 2k RPM for 10 seconds, and the temp drops right back. Until I replace the stupid plastic bottle with an aluminum one, I don't like it to go over 210. Mine may spin faster if it get's closer to 215, but mine never gets that hot. That fan should not spin that freely though when it is hot though....

My fan will spin about 1/4 Revolution by hand when warm. You can also hear mine roar when leaving stoplights once she is warm....

Cold, that fawker spins like crazy......

At what temp does the thermal fan fully engage? I put a 180 degree t-stat on there just for kicks (I know...lets not take this thread too far in that direction) and was wondering if that could affect the thermal clutch from fully kicking on? Seems like the only way the 180 could possibly be succesfull is if the thermal fan was replaced by an electrical one that comes on sooner. It is already getting over 210 with that T-stat and bad fan clutch anyway which has convinced me that the 180 no workie in the stock setup. Kind of like throwing snowballs into hell.


I will be putting a 195 back on after I flush the system.

Mikey said:

At what temp does the thermal fan fully engage? I put a 180 degree t-stat on there just for kicks (I know...lets not take this thread too far in that direction) and was wondering if that could affect the thermal clutch from fully kicking on? Seems like the only way the 180 could possibly be succesfull is if the thermal fan was replaced by an electrical one that comes on sooner. It is already getting over 210 with that T-stat and bad fan clutch anyway which has convinced me that the 180 no workie in the stock setup. Kind of like throwing snowballs into hell.


I will be putting a 195 back on after I flush the system.

Click to expand...

The t-stat deals with temps in the block, the thermal fan deals with temps in the rad.... Two separate things.

It's pretty well established that a 180 will only make a difference if everything else is 100% and able to keep the rad temps down below 180. if your rad temps are below 180, the fluids going into the block at that temp would bring the 180 stat into play. once the fluids in the rad go over 180, the fuid going into the block will be over 180, and the stat is out of the loop because it will stay open. you gotta fix the fan clutch.