ZJ vs XJ fan clutch
 

Recently installed the ZJ fan clutch in my 98' XJ and boy was it worth it! Swapped over to dual electric fans about 6 months ago and a few weeks ago I decided to go back to stock. I have had the ZJ clutch in for almost a week. Here are some things I've noticed so far.

PRO's: Cooler engine temp, cooler A/C, cooler engine temps, and did I mention cooler engine temps? No more overheating!

CON's: Slightly more noise but after a few days I don't notice it anymore, slightly worse MPG- (about 1/2 MPG)

Read a few peoples comments on here about the swap and they said there was a noticeable loss of power, personally I have yet to notice any between the XJ clutch and the ZJ clutch. However I did notice a deference between having dual electric fans and having the mech fan in there.

Mileage with the dual e fans was usually around 17.5 MPG, but the jeep still ran too hot for my liking- about 210 on the highway and 220 in town.
With the stock fan clutch I was getting on average 16.5 MPG, engine temps were usually at 210 all the time unless I was stuck in traffic or towing a trailer it would creep up to 220

With the ZJ fan clutch installed I've only gone thru 3 tanks of gas but so far the average is 16.1 MPG, Here's the good part... I haven't seen 190 on the temp gauge yet, at all, and that's including towing a 16ft trailer with a small car on it and sitting in traffic in 105* heat. Another pleasant side effect of the ZJ swap is my A/C is about 5* cooler (71*-66*)

All in all I'd definitely recommend anyone with cooling issues as long as you aren't worried about a little noise and a slight drop in mileage

Would you please tell me what the brand and part number ZJ fan clutch you used is???


I did a lot of searching for this info and could not find a ZJ fan clutch that would fit my 96 XJ. Lots of mentions to doing this so called upgrade but no data to go along with the name. Finally found one reference to a brand and part number only to discover that it was an HD for the XJ only, no connection to the ZJ.

I just went to autozone and asked for a 98 ZJ 4.0 fan clutch. I believe it's this one
http://m.autozone.com/autozone-mobil...pd92?id=265348

Should fit on your 96', I made the mistake of tossing the mech fan when I switched to dual electric so I pulled one from a buddy's 96' parts jeep and installed the new clutch on it.

Just make sure it's the ZJ clutch WITHOUT HD cooling and it should work

The HD fan clutch your referring to is NAPA #272310? It's definitely an upgrade over the oem one.

Yes, it is an upgrade over the standard clutch and is what I am currently running. But that Napa part number has no connection to the ZJ. Napa only lists it for the XJ. I'm looking to find out what exactly the brand, part number and ZJ application is for the fabled ZJ conversion fan clutch that is supposed to work so well (and maybe hopefully better than what I have now), that's all...

I still had my 31's on when I first put the ZJ fan clutch in. It helped a good bit, and I have a trans cooler in front of it now and it's hard for my trans to get above 160 degrees. I definitely noticed a slight loss of power. But now I have 33s and really want to regear...so I will probably leave it on there. My engine temps still hang around 195 ish when I have the electric fan on as well.

It's been the 272310 forever.

Napa's catalog is incorrect then.

What thermostat do you have in there?

XJ Upgraded HD Fan Clutch-
Hayden #2737 Amazon $41 free ship have used on 3 different Jeeps, works well
NAPA #272310 $43 quoted by many user, no personal experience, ?loud

^ that. The "ZJ upgrade" is the HD clutch used on the 2.5's.

http://www.napaonline.com/Catalog/Re...8004%205999999

A 195 :thumbsup:

I tried the ZJ fan clutch for one summer and hated it. The noise wasn't too annoying except for when merging on the highway, the thing still didn't unlock even when revved up to 3,000 RPM. Any higher and I could probably suck birds in through the radiator. :laughing:

The fan definitely pulls a lot of air, my problem was it pulls too much and didn't fix the problem. I still had temp spikes, and with the ZJ fan they were even more drastic. Before my Jeep would occasionally go to 215-220, but it mostly stayed at 210-212. With the ZJ fan, I could pull out onto a road and the fan would be 100% engaged, which would make the temp spike from 212 or whatever all the way down to 180*. Then on the highway it would creep back up to 215. The temp would swing back and forth, and in the winter it ran at 180* constantly. My buddy had similar results when we used one in his XJ.

My solution was to go back to the factory cooling system, but make it better.

I have a CSF 3 row radiator, and a Stant Super Stat 195* thermostat. I replaced the water pump with a new Mopar one even though the old one looked okay when I pulled it out. I replaced all the hoses and installed a new radiator cap along with a coolant flush. I used a new stock sized fan clutch from Autozone.

I'm going on 3 years with this setup, and I couldn't be happier. My temp stays steady, and the highest it has gotten has been 211* according to my scan gauge II. That was on a 95* humid day pulling a trailer up a hill. A few seconds later the temp went back down to 200*. My summer running temps are 200-206* and winter temps are 195-200*. I lost 1-2 mpg with the ZJ fan, and now I've been getting 17.5mpg, which I think is pretty good for a Jeep with a 2" lift and 30s.

What are the physical differences between the ZJ and XJ fan clutch?

Not much. Why?

Just curious why the ZJ clutch is "better".

Pulls more air, ever heard a 757 at take off? Lol

When the air coming through the radiator is hot enough to "engage" the clutch fan, the stock one goes 40% of driven speed whereas the ZJ one goes 60% of driven speed.

Im actually running a 2.5 4cyl fan clutch on mine. More clearence for csf three core . And still pulls better than stock xj did.

Is the ZJ fan clutch you are supposed to get part #272314? That's all I'm seeing but the other threads on naxja and whatnot say it's supposed to be 272310

NO! 272310 is the one you want for an XJ.

10-4. Thank you

As I mentioned in an earlier post, I have the Napa 272310 fan clutch and now also a CSF 3 row radiator. It does make a far amount of noise but not that bad. It does seem to work well in Southern Arizona heat as long as traffic stops are short and otherwise going at least 25 mph and 2000 rpm. Any speed slower than that and the temp starts climbing even with going to as low of trans and transfer gear as possible to keep the rpm up. As long as the ambient temps are 85 or less, coolant temp will stay below 215. Any higher ambient temps and I have to keep the speed up, turn the a/c off and turn the aux fan on, or park the jeep and shut it off until it cools off, or D all of the above. If this is supposed to be the best there is, I am quite disappointed in my first and possibly my last Jeep vehicle. I am now looking at converting to all electric radiator fans with the hope of controlling this temp problem. :wallbash:

I'm in Yuma and with the stock fan clutch and the electric fan on I can keep my temp at 190℉ pretty much all day. Even in the 115℉ heat it has no problem staying cool. I have the stock single core radiator, old style e fan, and hood vents.

Well, I guess my Jeep is a POS lemon... :dunno:

have you replaced your water pump and thermostat? Mine had that same issue when I got it a few years ago and replacing those parts helped.

I use all the above and have no cooling problems.

For you guys in AZ and the higher temps-
I also use 2 10" pusher fans in front of the radiator. These really help when off roading and crawling and sitting in traffic. Can wire to a switch of thermostatic switch. They work great to help get air flow across the radiator.

There is something wrong with your cooling system. You should track down what that is - the beefier fan clutch is likely only a bandaid for your problems. Search the forums there are many good posts about how to troubleshoot your cooling system.

To the OP, I looked into whether or not to swap in the ZJ fan clutch on my XJ pretty extensively earlier this year and I ultimately concluded (based on other's feedback) the following

I live in Virginia and we had one of the coldest winters in a long time last year (consistent days where temps did not rise above freezing). In the summer I am sure the ZJ fan clutch would be great (although my cooling system operates fine, and now I have wired a switch to my aux fan for those really hot days where I need a little extra cooling I can switch the fan on manually), but I know it would have kept my Jeep too cool in the winter, which is why I am just replacing my fan clutch with an OEM part (whenever I decide to get off my a$$ and install it).

A better mod may be adding an override switch to the aux fan. I have found this to work perfectly for me on those 95* plus days in the summer when the AC is pumping. Most of the time I don't need the extra air circulation, but it's nice to have. Whereas the ZJ fan clutch you don't have control over it, it's always operating.

I haven't heard of that but it makes sense, I live in kansas and it can get kinda cold here in the winter. I'll keep that in mind and might switch back to a xj clutch if need be. Thanks for the heads up

UPDATE. It got into the 30's today and the ZJ fan clutch mod kept the temps about half way between the 100 and 210 marks while on the highway. My heater also seems weaker on the highway as well, not sure if that is because of the fan clutch keeping the temps down or my heater core is clogged. I will be switching back to a XJ clutch for the winter.

See I don't get it. I have a new water pump and clutch fan with a toggle switch for my stock electric fan and my XJ runs at 210 all day. Never gets cooler. I don't want to rob more power away from the engine than is needed so an even more taxing fan clutch is out of the question for me.

My beef is that I've read several times that just changing the thermostat to a cooler one not only doesn't make any fdifference, but can also screw with the computer somehow in my 1998. Anyone else hear this? So I'm stuck with installing a larger rad and/or dual electric fans. How Tue hell is my XJ running so hot here in the East coast of Virginia? Its 60 degrees outside mid day and it still wants to run over 210 at a stop, idling for more than 10 minutes.

You have a fan shroud on there?

Have you done a full system flush? Sounds like some maintenance is in order. 210 is pretty normal for XJ's though. As far as the thermostat, you could install a 180 or 195, but nothing lower. It will not affect your gas mileage or computer settings, this is a popular myth out on the internet.

I went on line to Napa with the 272310 p/n and this is what it said:
P/N 272310 w/ Heavy Duty Fan Clutch,w/ Reverse Rotation Fan Clutch.

Someone said "make sure it's the ZJ clutch WITHOUT HD cooling"

So I am confused about that and should it be Reverse Rotation?

I live in southern MD and work in Northern VA so familiar with climate. Until recently I was running temps like you report. New water pump, rad, heater core and tstat and now stay under 210 consistently. Stock fan clutch and elec fan 291k miles. Rad tstat and water pump were done before heater core with under 210 temps. Also use good ole green antifreeze and distilled water somewhere close to 50/50 mix.

Spectra rad and heater core, new napa water pump and tstat.

Not sure what they were talking about. 272310 is the one I got from NAPA. I'm actually looking to get rid of it now because my rig has been cool and with winter coming, it's not worth the loss in horsepower.

I know this thread is older but for newer XJs running 210 is the correct operating temp from factory.

Pretty much.