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"HD" Cooling for YJ 4.0

8K views 85 replies 20 participants last post by  Louie4 
#1 ·
HD Cooling for YJ 4.0

Awhile back, I was looking to improve upon the electric fan set up I had on my 05 LJ Rubicon. It was unreliable; having failed once in the Arizona heat and once around town. These failures were both due to the relays and wiring, but I was not confident in the system after that, and decided I wanted to go back to a factory mechanical fan.

After researching several threads, I came across one that used a 9-blade Ford Explorer fan and an HD Fan clutch. After buying a new MOPAR radiator, the proper HD fan clutch for my LJ and the Reverse rotation 9-blad fan, fresh fluid and a MOPAR thermostat, the LJ temp stays at just under 210 on the factory gauge. This was true in Death Valley in July at over 120°, and the entire Rubicon Trail Trip in June. Along with excellent cooling, I have found that, when compared to the 5-blad fan of my friends TJ, the 9-blade fan was a lot quieter.

Gathering parts for my daughter's YJ 4.0 swap, I decided to see if I could provide the same HD Cooling for hers. After some research and speculation, I ordered the "AC Equipped" Fan Clutch for the 98 TJ engine I am using (as HD as I could find and the same will fit any 4.0 YJ) and the same 9-blade reverse rotation Ford fan. My concern is that the fan blade center opening would not fit over the stud base of the YJ fan clutch, as my LJ has the screw on style fan clutch. I took a gamble and ordered the parts.

The parts came in today and I immediately set about to see if it would work. It appears as if this set up will work. In the pictures below, you will see the fan blade on the fan clutch, as well as the part numbers for anyone thinking this may be a good fit for their build.

FAN: 620-112
Price: $25.99

Fan Clutch: 922737
Price: $36.99

I will report back once I have it installed. My fear is that I will need to find a more robust fan clutch, but I do not know this to be true at this time.
 

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#2 ·
Make note of the noise level for each.. I know there are trade offs for what you trying to do so it is expected.
I would have went with a triple core aluminum radiator and a good shroud also. I hate the metal fans jeep uses. They weigh too much.. But they are tough.
My racing days would would buy the lightest fan that we could get. There is one that is super light and tough and get this CHEAP.. With the lower RPM it pulled a lot of air.. At high rpm it flatten out so as to save power since the air coming in was more than enough.
Also marking this to watch how it comes out fer ya.
 
#3 ·
I am using a NOS Radiator and New 4.0 Fan shroud. Should be OK>

I guess if creating the ultimate HD Cooling thread, the mention of 3 core aluminum radiators would have to be discussed. I'm trying to simply improve the airflow, save a little weight, and keep the cooling stable as a rock. :highfive:
 
#5 ·
In AZ the relay went out. I had the fan on a dash switch with a relay. Relay went bad. Had no spares So I hard wired it to power.

The 2nd time the bade connector on the relay was losing contact with the blade and causing periods of non working and heat spikes. This was harder to diagnose. I gently smashed in the female connector and it worked ok, but it was rattling lose again so...

I just didn't trust the set up any more.
 
#6 ·
Interesting swap. Looking forward to finding out if this works on the yj. I currently have the hesco high flow thermostat housing and thermostat along with the gmb high flow pump with a stock metal fan setup that works very well for me but I have been looking for some different fan options without going electric. This may be what I need.
 
#7 ·
A fan discussion? I'm in.
Twice we have had to make trail repairs to electric fans which had one of the many components fail.
One of the failures almost ruined the owners engine.

We were at the dunes (the ones featured on Top Gear) and relay failed while the owner was letting it idle.
It sat, overheating, for 5 mins and he never noticed the fan, or lack of a fan. The gauge was PEGGED!
No electric for me, Thanks.

Also, when the fan isn't running, the underhood temps are soaring unless you are going fast and moving air.

I LOVE my stout steel mechanical fan. Huge deeply pitched blades cutting at the air. It one thing I don't think can be improved upon.
I also have a 3 core aluminum I got free in a manufacturers test.
They gave out 10 to residents of Las Vegas.
Easily out performs my original copper/brass which I still have.
Climbing sand dunes or crawling along in 115* heat all day and my gauge doesn't move.


I'm watching the thread though, I still have one more Jeep to maximize cooling and the fan looks interesting.
 
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#15 ·
Because it is on a factory fan clutch, on my LJ it fit very well just inside the stock 4.0 shroud I bought from Quadratec.

We will see on the YJ as I have not installed it yet. That said, I do not anticipate any issues as I will be removing the TC drop in favor of a CV shaft and SYE.

Electric for me! :) So the failure wasn't the stock fan setup, it was the mod?

Relay failure is usually wiring that is not done well or undersized electrical components. The heat issue I have heard about. Look at the hood vents they install. I had a friend with a tj Rubi that had soak issues that the louvers fixed.
I think it was just poorly done by me. the single hole self tapping screw I used to secure the relay allowed it to jostle around and that and the under-hood heat probably killed it. Then the same jostling probably caused the connector failure. Either way, Once I lost faith in it, I had to change it.

I like how the Poison Spyder louvers look, but I also don't like cutting perfectly good bondo-ed metal. My Hood may not be a good candidate for cutting :(
 
#14 ·
Electric for me! :) So the failure wasn't the stock fan setup, it was the mod?

Relay failure is usually wiring that is not done well or undersized electrical components. The heat issue I have heard about. Look at the hood vents they install. I had a friend with a tj Rubi that had soak issues that the louvers fixed.
 
#19 ·
UPDATE:

4.0 fan shroud came it yesterday from Quadratec. I wanted to verify that, like my LJ, the fan would fit the shroud.

It looks like it will. My hopes are that the tighter tolerances of the fan to the shroud will better pull and direct air when compared to the stock 5 blade fan with it's smaller diameter and blade gaps.
 

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#22 ·
This one has piqued my interest. I'm a OEM cooling system believer after going through many iterations over the last decade. My cooling system came off a stock '93 YJ to replace my electric fan setup. I also put a new water pump on and Mopar thermostat. My jeep runs cooler than it ever has. But I want to see where this one goes.
 
#23 ·
Guess I do not understand the need for the "cooling Upgrade" on the YJ. I live in the desert where the temperatures often exceed 100 degrees. We have several 4.0 YJ's in the club (including mine) and no one has overheating problems. Sounds like a complicated solution to a non-problem to me.
 
#24 ·
While I do agree that the stock 4.0 cooling system was (is) more than adequate to handle the needs of the 4.0, I submit that overall the 5-blade fan, while up to the task, can be improved upon in airflow, noise, and weight.

Replacing the fan clutch with the "HD" version will have the fan blades engaged more often, thereby moving more air. While it may not be necessary for optimal cooling of the radiator, it will help move air out of the engine bay, reducing heat soak somewhat better than the stock fan on a stock fan clutch.

Replacing the steeply pitched 5-blade metal fan with a less steeply pitched 9-blade fan should net more even airflow and draw over the stock, widely (unevenly) spaced 5-blade fan. The high density plastic ford 9-blade fan weighs less than the stock fan. How much? Great question. I will attempt to get a solid comparison and list it here.

Although not a huge factor, my hope is that like my LJ, the fan being less steeply pitched and having pronounced tips will be quieter than the stock fan.

I don't think you are wrong in saying the stock set up works well. I do think you are wrong in characterizing my "upgrade" as complicated. In fact, it's two very straight forward parts and about 30 minutes worth of work.

I do have the stock fan clutch and fan (a little bent, but should be fixable) and if I have time, I may just install my HD set up and try to somehow measure the noise and airflow and then swap back to the stock equipment and do the same. I'm not sure how scientific I can get, but I remind you that sometimes a small change can net great results.
 
#27 ·
X2. I want to know how it went?
It went like this:

1. Been making a few sets of Boomerang shackles for some /f12ers. Shipping this week.



2. Been finishing up the wiring harness on the 54 WILICON project and getting ready to fire it up.



3. Working Full time

4. Replacing the inner and outer tie rod ends, pitman arm, and idler pitman for the steering on my 03 Silverado

I have not had a chance to even clean off the engine to get ready to go through and replace all the gaskets, timing chain, sensors, plugs, injectors etc.

In about a week, the WILICON should be running, working lights, etc. and moved out of the shop for a long term (2 months?) shakedown before coming back to be blown apart again for finish welding some non-critical areas, bodywork, paint, frame detail, etc.

In that 2 month window, I only have to perform a 4.0 swap on my kids jeep, turn a 2wd cherokee into a 4wd cherokee with lift, tires, bumpers, etc. and sell it.

So updates here and details in a swap thread in about 2 weeks. :|

OH, almost forgot.. getting a new sticker machine sometime this week, I think... so making stickers again and shipping those out once I learn how to do that..
 
#32 ·
I have lots of pics and could slap up a recap thread, but it's been a long process and involved. So much so that I haven't felt like going through both at the same time. Perhaps once it is running I'll do a recap and highlight some of the challenges and solutions.
 
#34 ·
UPDATE:

WILICON is running and out of the shop

I have the engine cleaned and am going through. Did timing chain and gear, water pump, tstat, etc. Used a NAPA T-Stat 195° and a Duralast Water pump. Drilled bleed hole in T-Stat as usual.

POSSIBLY doing the swap next weekend because i have a few Fire department vehicles in the shop getting outfitted.

keep you posted.
 
#35 ·
UPDATE:

The installation, fit and everything went as expected.

Here's a short video of the fan running. As you can see it has plenty of clearance inside the stock fan shroud.



I'll have to admit, I have an issue with cooling. Once we got everything together and re-assembled, the jeep was running well over 240°.

I discovered quickly that the NAPA brand t-stat I bought wasn't opening up. Took it out and replaced it with another NAPA brand t-stat that I pre-checked in a cup of boiling water. Now I checked it, at work, using a microwave. I took two large coffee mugs and brought one to a boil. Set the new t-stat in the 1st cup of boiling water and left it there to "pre-heat" it. I then took the larger cup and boiled the water in the microwave for 3 minutes - a rolling boil. I quickly, using a pair of pliers, moved the t-stat from the hot water in the first cup to the boiling water in the second cup. It started to open up, but since the water was no longer under heat and cooling, it did not open up fully.

I did the same exact test on the bad t-stat and it didn't move at all. So, I am satisfied that the new t-stat is opening up. I installed it.

Once installed, the engine was running cooler, but still at the 220° mark on the temp gauge.

I got out my OHM meter and tested the temp gauge sender. At room temp it was reading 1940 OHMs. It should have been closer to 1700 OHMs. I went to the dealership and bought a MOPAR NOS temp gauge sender for $22. I installed it. Tested it at room temp, 1763 OHMs.

Ran the jeep and it made no difference. Jeep still idled at around 220° - that first white hash mark past 210°.

HMMM..

So I'm fairly confident that the temp gauge is correct, I have a good t-stat, fresh fluid, no leaks, new 16lb radiator cap, new hoses, new fan shroud, new fan, and new fan clutch.

With the engine reading 220° idling in the shop, I shut it off and grabbed the fan to see if the fan clutch was locking up. It moved very easily - just like it did when it was cold. Not good.

I had a MOPAR Stock fan clutch off the 98 TJ I got the engine out of. at room temp, it seemed stiffer than the Autozone one I had installed. SO.. I had my daughter swap it out after we installed her new neoprene seat covers and removed her flares for a fresh paint job.





Once installed, the jeep idled around the 215° mark, but would climb to the 220° mark when driven. This morning, I drove it to work in stop and go traffic for about 35 minutes. The temp would sit right at 220° until I started moving and the engine revved for a bit, then it would drop down to the ~ 215° point again, then right back up to 220°. Once I got to open freeway, at 70 MPH, the temp would creep it's way up to 240° again, and then dropped back down to 220° as I cruised off the freeway and took surface streets to my shop.

This tells me that I have a flow restriction - probably the 4-year-old AutoZone radiator I reused from the 2.5L engine. The 2.5L never ran hot. Never got above 200°. Solid as a rock on temps. SO I question if the radiator is the issue or not. It did sit empty for 2 weeks, but was safely set aside and undamaged.

Tonight I'm going to run a cooling system pressure check just to rule out a leak. If that checks out, I'm replacing the radiator. Luckily, I have a brand new Spectra AutoZone radiator sitting in a box, so it won't take long to test my theory. If the radiator doesn't get the temps to a solid 210°, I do have a factory TJ fan blade I could try... about the only thing left...

I'll keep everyone updated.
 
#36 ·
Interesting. Your problems sounds very similar to the cooling issues I had years ago. I went through cheap Zone fan clutches and thermostats as well as radiators. I also put a Taurus fan in for a bit. Finally, I went back to OEM parts minus the radiator and my jeep never breaks 200 degrees F. I'm curious to see how the radiator does.
 
#37 ·
The reason for the cooling system pressure check is that we took the 98 TJ block and, using a mag drill, drilled the hole in the boss for the temp gauge sender and tapped it NPT for the sending unit.

When we did this, we removed the rear freeze plug on the head to run a vacuum to collect any metal shavings that fell inside the water jacket. It is my belief that this freeze plug may not be properly sealed or that our sending unit hole may be leaking. I get 3-4 drips of coolant from back there after I stop each time. If one or both are an issue, they will need to be addressed. I have 3 days to figure this out before leaving on a 10 day cruise vacation. The day we get back, we drive the YJ to Idaho.

The pressure test may indicate that the rear freeze plug is leaking, which means we pull the engine to replace that freeze plug. If we do that, I'm swapping the radiator as well. If it's not leaking, and pressure holds, I'll swap the radiator anyways.

I had considered the 2-row aluminum Champion radiator, but with time restraints, the AutoZone on hand will have to do.
 
#38 ·
Thanks for the update. Please keep us posted.

FWIW all the strokers run https://www.amazon.com/CSF-2576-Rad...1-11&ymm=1993:jeep:wrangler&keywords=radiator

OEM `stat, clutch, WP and fan. Hi flow thermostat housing and 50/50 Mopar coolant.

195-200 all day 210-215 on the freeway spinning 3,000 @ any ambient temp. Drops back to 195 PDQ.

One important thing I`ve found is a well sealed overflow tank. IE no leaks.
 
#39 ·
It may well be I'm shooting for good enough at this point due to the time restraints of 3 days. Once she comes home again in Jan, I can update parts and bullet proof the system. The only great news is that, for the most part, she will be driving in cold weather and snow from about October on... so there's that.
 
#40 ·
oh yeah, less radiator effeciency in the winter is fantastic for the inside heat. I definitely use the wood panel to block 1/4" of my radiator if I'm not going to be on the highway.

I think I'm in the same boat too though, my engine temp has been creeping up lately. Pretty sure the radiator is starting to clog over time :( Mine is original, I can't believe your new radiator is already going though...
 
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