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Fan clutch show down: standard duty 4.0 vs ZJ fan clutch (same as 4cyl)
Stock XJ Cherokee Tech. All XJ Non-modified/stock questions go hereXJ (84-01)
All OEM related XJ specific tech. Examples, no start, general maintenance or anything that's stock.
Fan clutch show down: standard duty 4.0 vs ZJ fan clutch (same as 4cyl)
Fan clutch show down: standard duty 4.0 vs ZJ fan clutch (same as 4cyl)
I swapped in the 4cyl XJ fan clutch (same as ZJ fan clutch, I'm told) on my '97 4.0L a few days ago. I got it from Oreilly's for $40. In the rest of this post, I'll refer to it as the "heavy duty fan clutch." It is slightly bigger and had cooling fins all over it.
The heavy duty fan clutch was much much louder and pulled much more air for sure. It also lowered my fuel economy a fair amount.
with XJ 4.0 fan clutch: 16.13 mpg
with XJ 4cyl fan clutch: 14.27 mpg
^^^ those numbers are not super robust because that was only one day's worth of driving (about 10 miles) for each fan clutch, and around the city only. Highway numbers might not differ as much as city driving.
As for engine temperatures: with the heavy duty 4cyl fan clutch, it did seem to keep temperatures down a little more, and I don't think the temperature ever got above 200°F (the high that day was 92°F). With the normal 4.0 fan clutch, the engine temperature was staying at 210°F but it was also a lot hotter that day (high of 100°F). Of course, the engine temperature is supposed to be at 210 for best performance and efficiency. That probably had an effect on the MPG numbers.
One last point to be made: throttle response. When I first put on the heavy duty clutch, I thought I could feel a lose in power. After taking it off and before putting the normal one back on, I drove around the block with NO fan clutch (engine was cold started) to see if it felt different, and to be honest it didn't feel much quicker. With the regular fan clutch back on, again I didn't feel much change in throttle response. So I don't know...
So I would say that if your jeep is struggling a little while crawling around the hot desert or the LA traffic with the AC on in the middle of summer - go with the heavy duty fan clutch but don't be surprised if it makes her a little more thirsty.
I'm now running with the normal duty 4.0 fan clutch for now, will keep the heavy duty fan clutch in case I need it if crawling around the desert one day. I also have developed a severe hatred of those four fan pulley nuts...
Hope this helps someone out there!
Question: why does the 4cyl XJ need a larger fan clutch?? Maybe the pulley is a different size?
Question: why does the 4cyl XJ need a larger fan clutch?? Maybe the pulley is a different size?
Necro post but if anyone ever wonders why the 2.5L XJ has a heavier duty fan clutch it's because they don't have an E-Fan. The Mech fan has to do all of the work.
See now this makes me feel better.
Awhile back I determined that my fan clutch was not operating as it should.
Despite not having any cooling problems I decided to replace it anyway.
So being aware of the ZJ upgrade I asked my boss at the store what he thought.
Not a Jeep guy but definitely a car guy. Kind of guy when he talks you pretty much listen and do what he says.
So he says you don't tow and you are not having any cooling problems.
It is going to be noisier and your MPG might tank.
So no.
Glad I listened.
How did you calculate fuel mileage when you only drove 10 miles? You need to hand calculate when you fill up, if your going by the digital readout that is often not accurate.
How did you calculate fuel mileage when you only drove 10 miles? You need to hand calculate when you fill up, if your going by the digital readout that is often not accurate.
Very true. Can't determine squat in 10 miles.
But as far as a digital readout goes I come to find out that for a 320 mile round trip my overhead was pretty right there with my calculations.
Averaged just under 22 MPG on that trip and crossed the GWB both ways.
Going breezed right over the bridge. Coming home later not so much. LOL.
See now this makes me feel better.
Awhile back I determined that my fan clutch was not operating as it should.
Despite not having any cooling problems I decided to replace it anyway.
So being aware of the ZJ upgrade I asked my boss at the store what he thought.
Not a Jeep guy but definitely a car guy. Kind of guy when he talks you pretty much listen and do what he says.
So he says you don't tow and you are not having any cooling problems.
It is going to be noisier and your MPG might tank.
So no.
Glad I listened.
There's a test procedure for the fan clutch in the FSM. One is a basic test that just involves spinning the fan cold by hand. The other involves drilling a small hole in the fan shroud and inserting a temperature probe, tarping off the grille and getting the area behind the radiator up to 190 degrees.
TESTING
If the fan assembly free-wheels without drag (the
fan blades will revolve more than five turns when
spun by hand), replace the fan drive. This spin test
must be performed when the engine is cool.
For the following test, the cooling system must be
in good condition. It also will ensure against excessively
high coolant temperature.
WARNING: BE SURE THAT THERE IS ADEQUATE
FAN BLADE CLEARANCE BEFORE DRILLING.
(1) Drill a 3.18-mm (1/8-in) diameter hole in the
top center of the fan shroud.
(2) Obtain a dial thermometer with an 8 inch stem
(or equivalent). It should have a range of -18°-to-
105°C (0°-to-220° F). Insert thermometer through the
hole in the shroud. Be sure that there is adequate
clearance from the fan blades.
(3) Connect a tachometer and an engine ignition
timing light (timing light is to be used as a strobe
light).
(4) Block the air flow through the radiator. Secure
a sheet of plastic in front of the radiator (or air conditioner
condenser). Use tape at the top to secure the
plastic and be sure that the air flow is blocked.
Fig. 40 Typical Viscous Fan Drive
(5) Be sure that the air conditioner (if equipped) is
turned off.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A DIRECT
LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR FAN. DO
NOT WEAR LOOSE CLOTHING.
(6) Start the engine and operate at 2400 rpm.
Within ten minutes the air temperature (indicated on
the dial thermometer) should be up to 88° C (190° F).
Fan drive engagement should have started to occur
at between 74° to 82° C (165° to 180° F). Engagement
is distinguishable by a definite increase in fan
flow noise (roaring). The timing light also will indicate
an increase in the speed of the fan.
(7) When the air temperature reaches 88° C (190°
F), remove the plastic sheet. Fan drive disengagement
should have started to occur at between 57° to
79° C (135° to 175° F). A definite decrease of fan
flow noise (roaring) should be noticed. If not, replace
the defective viscous fan drive unit.
I popped the coin for an actual OEM Mopar standard duty fan last year which works very well, but I've still got my Hayden (2737) 4cyl XJ fan on the shelf.
There's a test procedure for the fan clutch in the FSM. One is a basic test that just involves spinning the fan cold by hand. The other involves drilling a small hole in the fan shroud and inserting a temperature probe, tarping off the grille and getting the area behind the radiator up to 190 degrees.
I popped the coin for an actual OEM Mopar standard duty fan last year which works very well, but I've still got my Hayden (2737) 4cyl XJ fan on the shelf.
I accidentally came across that video that I post from time to time about how a properly working
fan clutch, when the engine is hot, will stop almost immediately when you turn off the engine.
When it just spins not so good.
Despite not having any problems I replaced it with the Napa one. Which I am pretty sure is a rebranded Hayden.
Will have to remember to check it one of these days. LOL.
I replaced my original fan clutch a few years ago with one from Rock Auto. It seems to work well and pulls a decent amount of air. For extra cooling while towing or off-roading, why not just wire up your e-fan with an override switch?
Here's a clip of my setup. You can see how the fan works when the clutch is fully engaged and how I've got my aux e-fan wired up.
its been reported by users in parts of Australia where the temp regularly exceeds 100F that this is an extremely effective mod
Thorough flushing the block is the other thing that is needed on an older vehicle
That's a good point. I think one reason people see overheating on an otherwise functioning cooling system is the rust/scale buildup inside the block/head and radiator limits heat transfer.
07-05-2018, 09:52 AM
Fan clutch show down: standard duty 4.0 vs ZJ fan clutch (same as 4cyl)
