Ultimate XJ Cooling System

Anyone else think the old Shistler/Jeep XJ OEM cooling design may be a tad bit inadequate? If you live and drive in the deep south you do!!!!

The main clutched mechanical fan is small and offset to one side of the radiator and the electric AUX fan is only activated if the AC is on or the temp reaches 220*F. It will turn off when it reaches 200* again. This makes them sit at 220F* in the summer and have issues with heat soaking the fuel in the injectors and lock them up between a 15-30 min. sit after running at operating temp.

Earlier this year I decided to give the cooling system design the benefit of my doubt and I replaced everything with quality OEM style parts including the radiator with a very high end all metal brass high flow, new water pump, fan clutch, 180* Tstat, Tstat housing, flushed and replaced all fluid

After all this the system did not change its behavior. It does run great and cool at highway speeds regardless of ambient temp but when you come to a stoplight or pull into a parking lot it runs very hot. over 220*.

It is not overheating but sits around 220*. If you you let it sit for a good 5 minutes it will eventually start to cool down to around 210*. If you shut it down at 220* it will be at almost 235* when you restart it within 10 minutes.
It has not overheated or boiled over at all but it has caused a few pinhole leaks after a few months in the tstat and water pump housings that are driving me nuts. I have re-RTVd both several times this year and it is wearing me out walking by my XJ and smelling coolant every few months.

All of what I described is considered normal operating temps and ranges for an XJ according to Jeep, Alldata, and every other tech resource available.

Every XJ we have worked on in our shop has acted the same way regardless of age or condition.....

With the lift, tires, and armor I recently added, this situation has not been improved so after months of research I finally decided to upgrade.

A lot of people go with a ZJ fan clutch that will give you more mechanical fan output when hot at low RPMs. The problem with this is the fan is at a much higher lockup rate and will make the engine use more fuel at highway speeds. I didn't want to go this route. Others tend to go cheap an throw some hood vents in it and call it a day. Where this would probably alleviate most of my problem, I am just not a fan of rain and snow falling directly into my hood.

The 4.0 in the XJ easily needs 2500-3000 CFM similar to a smallblock V8 like a GM 350. The stock 15" fan pulls around 700 CFM at idle and approx 2000 CFM at 2500 RPMS. The stock electric fan pulls about 800 CFM. This is not enough to keep this coolant system down at or below 210 on a regular basis with the 100*F+ temps we get down here in Texas.

After a lot of research due to the unavailability of a good "kit", I decided to replace both fans with a dual electric 13" fan setup from Derale with a DIF variable speed fan controller. The fans are a puller setup and will pull 4000CFM at 25 amps per fan. This is a lot of amperage and draw on the batter system so I didn't just want an on/off type typical temp switch. Instead I went wanted to go with a variable speed controller. I was only able to find 2 good adjustable fan controllers, a flex-a-lite and a DIF. Unfortunately the cheaper flex-a-lite can't handle more than 45amps which I called to confirm with flex a lite. I then ordered a DIF variable speed fan controller which can handle up to 60 amps. I am going to program the DIF to turn the fans on at about 185-190* and try to keep my temps below 200* at all times.

I also ordered a FlowKooler high flow water pump that doubles the water flow at idle and a Robert Shaw high flow thermostat. After replacing the hoses, pump, and tstat I started modifying the fans to get them to fit in the 12" tall 30" wide space behind the radiator. The Derale kit is the smallest setup I could find with enough CFM to cool the engine. It is approx 28" wide and about 14.5' tall. It is also 3.25" deep which needed to be trimmed as well. Fortunately the ABS plastic the fans are made out of is strong so even after removing this much material they weren't flimsy. I pretty much cut all the extra plastic I could to get them to set inward towards the radiator, away from the pulleys as much as possible, and low enough to clear the hood line.

I am not finished yet. I still need to cut out some HD rubber to put on top of the fans and bolt down under the top of the radiator to cover the gap on top. The fans clear the hood and are bolted to the backside of the radiator brace on top and bottom so they won't move at all. I will get the wiring done shortly and post up the final pics and the mess of wiring and programming required with the DIF controller.

Here are some pics of the progress and the album:http://s127.photobucket.com/albums/p145/06unlimitedrubi/XJ Ultimate Cooling/

very nice! I still dont trust electrical fans as the sole cooling source. My buddy with a Mercedes convertible just had his go bad and had to get towed (bad electric motor).

How do you like the flo cooler pump? I heard its not a whole lot different then the OEM 4.0 pumps, therefore not worth 2x the price.... ever look into the HESCO water pump w/ aluminum impeller?

The real problem with the OEM design is that the stamped steel impeller can come apart and dig into the block.

looking at those fans you may be able to just turn them on and drive the jeep without starting the engine.
I have one electric in my jeep and when I shut the engine off I can still hear it humming. That is going to sound like a jet engine under the hood. I hope it keeps it cool. One word on the flow kooler though, I had one for 4 years that I just replaced because coolant was coming out of the weep hole. It doesn't really do much more. When you get it compare it side by side with your OEM pump, the real noticeable difference is the plate that is riveted on to the impeller. There is a thread in here somewhere about the Flow Kooler pump and most guys said it didn't do much for the amount it costs. But in reality what ever keeps the needle at 210 or lower then go with it.

from the looks of it your cooling issues may have stemmed from your winch covering your entire radiator instead of just making the mistake of living in TX:repair:

I ran about 170-185deg this summer (which was hot for washington) 90 or so out side and all I did was install a 130deg tstat added a bottle of water wetter and ran the stock electric ran off a switch. cost me about $25.

We have installed the flowkoolers on customers Jeeps that wanted an upgraded pump in the past. Never had any issues with them. No they do not magically make your cooling system perfect but they do help a little. Which is what the XJ cooling system needs... a little help. To be honest I feel that stock cooling systems are generally fine for the most part and that people that have problems with them just need to check them out because they have a problem somewhere. That is not the case with this Jeep. I manage one of the most hardcore Jeep/Rock shops in TX and I can assure you we understand how to install a coolant system. I have other Jeeps like my LJ 4.0 with no issues with the stock cooling system. The XJ just needs to come down about 20* at idle and stopping speeds.

As far as the Flowkooler cost is concerned, we are a Brassworks/Flowkooler/Robert Shaw dealer so it is not a big cost to me. I decided it was worth doing since I had it apart anyway. As far as the design of the pump is concerned, your right that it basically looks the same for the fins but with a plate welded to it, except it also has a slightly different internal flow shape and design. I will have to dig up another one and snap some pics. By no means is it the answer to all my problems, but every little bit helps.

As far as the winch and bumper are concerned.... those were only added in the past couple of months with my bigger lift and 35s..... These problems I described with the XJ stock system have been prevalent on my XJ since it was stock when I bought it about a year and a half ago. I rebuilt the entire coolant system in Feb. this year with better than stock high end OEM replacement parts with the Jeep on a 32 and a 3.5" lift with no improvement before I ever added the bumper and winch. This thing actually runs extremely cold and stable at 185*-190* on the highway or over 40 mph with no problems. It just wants to heat up as you come to a stop and the cooling system pumps and fans slow down with the engine still hot and it can't keep up.

What most of you damn YANKS don't understand about the south and heat is that it's not dry heat like in Arizona or Cali. Or like when it's 80* or 90* up north and it's a "heat wave" and everyone is miserable. In Texas it's 80-90% humidity even when it's only partly cloudy and 100*+ for over 90 days a year. If you have never lived here, you truly have no idea what the rest of us are talking about. My old construction equipment (brand new dozers and loaders) would overheat when I took them down to Houston when it was 90* outside because of the 100% partly cloudy humidity.

Hence the 4000CFM fans and the VARIABLE SPEED CONTROLLER.... and by the way.... these are worth every penny as they are the quietest fans we have ever heard. They are easily as quiet as the stock fans but will absolutely blow you over!!!

I will post up some more pics and video Mon or Tues when I get everything finished.

this looks awesome, thanks for all the info. the stock fan system blows.

What's the part number to the fan that you used?

I used the following:

Derale 16928 dual fan 4000cfm
Flowkooler 1747 high flowkooler
Robert shaw 180* stat
DIF variable speed fan controller from frsport.com

I'll post up the programming sequence, wiring, rubber fan/gap cover early next week.

Thanks for the write up - I use to live right around the corner from you (so to speak) in Carrollton - man I miss that area.
Next time I'm down there I'll drop by and say hello.

Just a note your link in your signature is hosed and tries to lead us here:


http://naxja.org/forum/www.at-fab.com

Flowcooler is nothing buy hype. Make your own with a $1 piece of aluminum sheet and a couple pop rivets on a stock new waterpump and you will have something a lot more durable.

Where did you get the flow specs on the stock fans? People have been asking for that for a long time here and no one has been able to cite a reliable source.

That Derale is 4000 CFM for the PAIR - not each.

For a controller you should look at the unit from DC Controls - from a features, functions and reliability standpoint is beats everything else on the market.

DieselSJ said:

Flowcooler is nothing buy hype. Make your own with a $1 piece of aluminum sheet and a couple pop rivets on a stock new waterpump and you will have something a lot more durable.

Where did you get the flow specs on the stock fans? People have been asking for that for a long time here and no one has been able to cite a reliable source.

That Derale is 4000 CFM for the PAIR - not each.

For a controller you should look at the unit from DC Controls - from a features, functions and reliability standpoint is beats everything else on the market.

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As I said before, the FlowKooler is not the same as a stock pump. I will post up some pics of the oversize internal passages compared to stock so you skeptics can see there is a difference, however small it may be. I agree it may not even be noticeable but if it happens to push any more fluid than stock at idle that will help me.

This is from Bosche on the stock electric fan....

Bosch GPB 12v 13.5Amps
12" dia x 3.25" depth


.25 Cubic Meter Per Sec
900 Cubic Meter Per Hour
530 Cubic Foot Per Minute

I don't know how I am flawed in what I said about the operation of this coolant system but here's some alldata info in case you are unaware....


OPERATION
Electric cooling fan 4.0L: With or without A/C request the electric fan will come on only when the coolant temperature is at least 106°C (223°F) , and will remain on until the coolant temperature drops to 103°C (217°F) or below. Regardless of coolant temperature, when air conditioning system pressures reach 2068.5 ±138 kPa (300 ±20 psi) the electric fan will engage and continue to run until the A/C system pressure drops to 1620.3 kPa (235 psi) minimum, then the electric fan will shut off.

As per the stock 15" fan I will have to just refer to general fan knowledge which you can spend your own time researching. We have learned the following from years of building hundreds of custom on and offroad vehicles.....

The average 15" mechanical fan with a 60% lockup fan clutch will pull around 750-1000 cfms at idle, approx 2000-2500 cfm at 2500 rpms and appox 4000-5000 cfms at 5000 rpms.

Maybe you didn't read all of what I said about the desert not being the same as the humid heat we have in this part of the country. Which also means you probably missed where I said my Jeep runs ice cold already at highway speeds so that is not my problem either. If you read carefully you would see that I am just tired of how hot the engine runs at stop and idle even in perfect stock condition.

I never stated that my Derale fans were 4,000+ CFM each, they are 2000 cfms per fan for a total of 4,000 cfms. Derale's flash site sucks so I will refer you here: http://www.jegs.com/i/Derale/259/16928/10002/-1

I am familiar with the DC controls fan modules. They are good but they didn't fit the operation I wanted for this application. Since it seems you don't really read most of what people post I will tell you again to check out the DIF from FRsport.com. For this application, this seemed like the most logical fit. It will read off of any 2 wire temp sensor so you don't have to add one. It will give you the option of variable speed with a range of 20%-100%. It will allow you to bypass to 100% with a separate ground switch. It has a cool down option which will leave the fans on for 30 seconds after shut down to help keep temps cool and avoid heat soak.

It has nothing to do with what you need for your "Race XJ" Laugh..... I am not just another dumbass noob posting about a coolant system..... I am a professional Jeep/offroad mechanic who happens to manage a very well respected shop that builds everything from stock rigs to full blown KOH rigs......

Sorry, I just get annoyed with people like you that just come on here to talk shit and try to look smart...... Remember, I do this for a living and I actually get paid for my Jeep knowledge everyday...... It's not just a "Hobby" for me like it is for you..... I get paid to be correct about Jeeps.....

RARRRRRRRRRRRRRRRRRRRRRRRRRRRR!

:thumbup: Looks like a nice, clean setup with some sweet fans. How much do you have into the setup so far? I was a cheapass and simply went with a pair of generic 10" fans to replace the mech fan. It works good, on those 90*/90%+ days it can get a little hot and will run around 220*. Once I add in an override switch for the aux fan to have all three going, I shouldnt have to worry about it anymore.

AT FAB XJ said:

Sorry, I just get annoyed with people like you that just come on here to talk shit and try to look smart...... Remember, I do this for a living and I actually get paid for my Jeep knowledge everyday...... It's not just a "Hobby" for me like it is for you..... I get paid to be correct about Jeeps.....

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I hope for your business's sake, you don't talk to your customers that way. :looser:

If I talked to customers that way I wouldn't have a business to run. I am just sick and tired of forum abusers and Dbags that are only on here as an alternate reality they can have online where they blow up peoples threads. This kind of stuff is the reason why I have avoided posting techs and builds. This is also the reason for threads about why join naxja and treat everyone the same as you want to be treated. I wouldnt call going on someones build thread who is trying to share tech and install info and challenging everything they are doing without any reason a good post or good forum use. Sorry if I over-responded but I'm sick of these kind of Dbags on forums!

Can you cite the source of your fan information, gratzi.

AT FAB XJ said:

I rebuilt the entire coolant system in Feb. this year with better than stock high end OEM replacement parts with the Jeep on a 32 and a 3.5" lift with no improvement before I ever added the bumper and winch. This thing actually runs extremely cold and stable at 185*-190* on the highway or over 40 mph with no problems. It just wants to heat up as you come to a stop and the cooling system pumps and fans slow down with the engine still hot and it can't keep up.

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Might I suggest reading a guide on burping the renix cooling system.


http://www.lunghd.com/Tech_Articles/Cooling/BurpAirMod.htm

That knowledge should help your company be more efficient. Unless you do excessive replacements work for the labor rate

If what you said is true then this IS your problem the renix isn't as bad as people make it out to be and a rebuilt system properly burped would work great.

He doesnt have a Renix.

Exxon Valdez Jeep said:

He doesnt have a Renix.

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Doesn't matter. He still needs to burp the system. But then again, he gets paid to know his stuff, so he must have done that already.