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ZJ Fan conversion?

O

Onyx Dragon

NAXJA Forum User
Location
Manassas Park, Virginia
Hey gang, I tried searching for this but was unsuccessful. I have a 1995 XJ with the 4.0, I need to change my fan clutch, and someone told me to convert to a ZJ fan. What is the difference between the belt driven ZJ fan and the XJ fan? What parts will I need for this? Thanks!
 
The ZJ one is longer(closer to the radiator) & the clutch is bigger.
HPIM1894.jpg


Unbolt fan, bolt to new clutch & bolt in. It is harder to get the ZJ in. Napa # 272310. HTH. JIM.
 
I think it was worth it. The fan is the stock one so it doesn't hit the shroud. With the larger clutch it spins the fan faster, which makes it more efficient. Just make sure the motor mounts are in good shape, I have heard of the fan getting into the rad. with poor ones. JIM.
 
ILLXJ said:
I think it was worth it. The fan is the stock one so it doesn't hit the shroud. With the larger clutch it spins the fan faster, which makes it more efficient. Just make sure the motor mounts are in good shape, I have heard of the fan getting into the rad. with poor ones. JIM.
Click to expand...

Oh, ok, so it's the stock XJ fan with the stock ZJ fan clutch. Gotcha. Someone just said do the ZJ fan conversion to me, so I thought they meant the entire fan.

The mounts are about a year and a half old, so they should be in good shape still. I replaced them myself.
 
Onyx Dragon said:
Oh, ok, so it's the stock XJ fan with the stock ZJ fan clutch. Gotcha. Someone just said do the ZJ fan conversion to me, so I thought they meant the entire fan.

The mounts are about a year and a half old, so they should be in good shape still. I replaced them myself.
Click to expand...

You should be fine then. JIM.
 
subscribed. i'll add this mod to my list of considerations for improved cooling.
 
ehall said:
http://www.naxja.org/forum/showthread.php?t=962512
I removed the HD clutch since it was keeping the operating temp too low. Mileage was poor from the computer trying to run rich and the heater wouldn't warm up.
Click to expand...

I had the same results using the ZJ fan clutch on my 01 DD.
It worked too well in cool weather and would not allow the engine to warm up. It engaged the fan all the time and made a lot of noise, even when cold. It also cost 2 MPG on freeway trips.
It is the ticket for a trail only rig when used in warm weather.
I re-installed the stock clutch and saved the ZJ clutch for summer only 4X4 trips.
 
Both the ZJ HD fan clutch and the standard XJ fan clutch run at 20-30 percent of shaft speed when disengaged.

Both the ZJ HD fan clutch and the standard XJ fan clutch will engage for a short time when cold due to the silicon fluid of the clutch seeping out of the reservoir when sitting, so both clutches engage for a short time until the fluid spins back into the reservoir.

Both the ZJ HD fan clutch and the stardard XJ fan clutch start to engage when the air temperature hitting the bi-metal spring on the front of the fan clutch is at 170 degrees--at that time the engine coolant at the water pump outlet is about 200 degrees.

The standard XJ fan clutch, when engaged, spins at 60-70 percent of shaft speed. The ZJ HD fan clutch, when engaged, spins at 80-90 percent of shaft speed--it moves more air and you will hear it.

Note that any MPG loss will occur only at those times when the fan clutch is engaged--idling, stop and go, 4x4 use. When moving at speed the fan clutch will not engage if the air temperature hitting the bi-metal spring is under 170 degrees.

Also, the ZJ HD fan clutch measured "depth" is identical to the standard XJ fan clutch. If you have a thicker radiator the clearance may be reduced, but the XJ standard fan clutch will also eat the radiator if your motor mounts are bad enough.

PS--if you find yourself running too cold in the winter, cut a piece of cardboard and put it in front of part of the radiator to reduce airflow and increase your temps. Remember, until the air temperature hitting the fan clutch bi-metal spring is at 170 degrees, the fan clutch is not starting to engage, so cold weather DOES NOT cause the fan to operate any more than the disengaged 20-30 percent of shaft speed.
 
Last edited:
joe_peters said:
Both the ZJ HD fan clutch and the standard XJ fan clutch run at 20-30 percent of shaft speed when disengaged.
Click to expand...
[FONT=&quot]I'm interested in where you found this information. [/FONT]

joe_peters said:
Both the ZJ HD fan clutch and the standard XJ fan clutch will engage for a short time when cold due to the silicon fluid of the clutch seeping out of the reservoir when sitting, so both clutches engage for a short time until the fluid spins back into the reservoir.
Click to expand...
[FONT=&quot]The stock clutch acts this way. The ZJ never seems to disengage, it is always howling. It just get even louder during extremely hot conditions[/FONT]

joe_peters said:
Note that any MPG loss will occur only at those times when the fan clutch is engaged--idling, stop and go, 4x4 use. When moving at speed the fan clutch will not engage if the air temperature hitting the bi-metal spring is under 170 degrees.
Click to expand...
I make the same 6+ hour drive north up I-5 from LA to San Jose almost monthly. With the ZJ clutch, I lost 2MPG on this drive twice and the continuous noise was bothersome. When I re-installed the stock clutch, the mileage came back up to where it had been before.

If the ZJ clutch I used (from Napa) was the only one that acted this way, it would appear that it was a defective but there are at least three of us on Naxja that have had the same experience. As usual, YMMV

BTW, have you used a ZJ clutch on your XJ?
 
After I went through all this in this thread:

http://naxja.org/forum/showthread.php?t=1009756

joe_peters talked me in to getting the ZJ HD clutch (and NOT the ZJ MAX clutch). So, stock XJ fan with ZJ HD clutch solved my creeping problem and I really don't notice any "howling" or increased noise other than the frikken HURRICANE in my engine bay.

Since I upgraded it hasn't gone over 210, towing, wheeling, grades, traffic. It just sits there just under the 210 mark all day long.
 
ParadiseXJ said:
After I went through all this in this thread:

http://naxja.org/forum/showthread.php?t=1009756

joe_peters talked me in to getting the ZJ HD clutch (and NOT the ZJ MAX clutch). So, stock XJ fan with ZJ HD clutch solved my creeping problem and I really don't notice any "howling" or increased noise other than the frikken HURRICANE in my engine bay.

Since I upgraded it hasn't gone over 210, towing, wheeling, grades, traffic. It just sits there just under the 210 mark all day long.
Click to expand...
.
Maybe what I call 'howling' is the same as what you call a 'frikken HURRICANE in my engine bay'.

There is no question that the ZJ clutch works, it just works too well, IMO, for a DD especially in cold weather. In the winter, your XJ may never warm up to its normal operating temperature, which isn't good. It was designed to run at 210 and that's what the computer wants to see.
 
lazyxj said:
.
Maybe what I call 'howling' is the same as what you call a 'frikken HURRICANE in my engine bay'.

There is no question that the ZJ clutch works, it just works too well, IMO, for a DD especially in cold weather. In the winter, your XJ may never warm up to its normal operating temperature, which isn't good. It was designed to run at 210 and that's what the computer wants to see.
Click to expand...


Then you have a problem with your thermostat !
In a properly operating cooling system, it's the thermostat
that determines the operating temperature.
If you think about it for a couple of nano-seconds it'll make sense.

With a 195* thermostat, it will be CLOSED when the engine (coolant) temperature is less than 195*. That means NO coolant circulating through the radiator and, as such, it doesn't matter how much air a fan is pulling, it's not going to affect the engine temperature if the thermostat is closed.


:)
Fred
 
When I did mine I did the clutch, water pump and thermostat. Now even at full throttle the SOB doesn't shut up. It sounds like a damn freightliner, and w/ my air intake whistle it REALLY does. So in other words my fan clutch is constantly engaged, aaand my temp usually doesn't hit 210 anymore...195 all the time. Upon initial warmup it hits 210 once then drops to 195 and sticks there. As far as I'm concerned its all gravy. Hasn't affected any drivablility or gas mileage.
 
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