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  #46  
Old January 1st, 2010, 12:06
CherBear CherBear is offline
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by MT Mike View Post

(P.S.: You should listen to those who have been around the XJ a little longer than you. Richard knows what he is talking about.)
x2
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  #47  
Old January 1st, 2010, 12:27
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by BarFlyFisherman View Post
Goatman - You don't need to be a condenscending d!kh#@d.
Yes he does!

Sometimes it is the only way to get people to learn, unless the person is just too stupid!
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  #48  
Old January 1st, 2010, 15:47
CherBear CherBear is offline
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by Goatman View Post
While a bad thermostat, bad clutch fan, or bad aux fan will cause overheating, the majority of overheating in XJ's is caused by a partially plugged radiator.
Yes, I know all too well...




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  #49  
Old January 1st, 2010, 16:29
xcm xcm is offline
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Re: XJ Cooling System Deficiencies & Solutions

thank you goatman and cal for keeping this thread unretarded.
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  #50  
Old January 1st, 2010, 17:28
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kastein kastein is offline
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by Goatman View Post
It is true that XJ cooling systems are prone to problems. The cause, from the mouth of a factory Jeep engineer, is from the shape of the radiator. The styling of the XJ requires a long radiator but with a short height, which limits it's overall capacity to cool. The XJ radiator has fewer tubes but the tubes are longer, which is inefficient. A radiator with more, but shorter, tubes will cool better. Once the water travels so far down the tube, it won't really get any cooler, so the extra length is wasted and the radiator is inefficient.
Makes me wonder, personally - why not build a radiator with vertical tubes? Results in more tubes in parallel (also shorter so the wasted length at the cool end doesn't come into play.)

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Originally Posted by jeeperjohn View Post
I have found that in an auto XJ, the transmission fluid transfers alot of heat back into the coolant when running up a steep hill. This can actually make the engine overheat because it counteracts the cooling being done by the radiator. It helps a great deal to use an auxilary (like a B&M) tranny cooler and don't run the tranny fluid through the radiator.
I have also noted this. I found that if I was cruising along at ~50+ mph, I'd be doing fine at 210 degrees, but if I stopped quickly after doing this (like say getting off the highway and hitting a red light right off the ramp) the temp would spike up to 20-30 degrees above, nearly going into the red. I have an aux cooler I haven't gotten around to installing yet, it's going in soon. For the moment what I do is throw it in neutral as soon as I end up stopping and rev the engine up to around 1100-1400rpm so the mechanical fan helps it out a bit. I may also have an issue with my electric fan, not sure, I need to check into that more thoroughly before I consider doing anything goofy and drastic like the OP.
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  #51  
Old January 1st, 2010, 17:42
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by kastein View Post
I have also noted this. I found that if I was cruising along at ~50+ mph, I'd be doing fine at 210 degrees, but if I stopped quickly after doing this (like say getting off the highway and hitting a red light right off the ramp) the temp would spike up to 20-30 degrees above, nearly going into the red. I have an aux cooler I haven't gotten around to installing yet, it's going in soon. For the moment what I do is throw it in neutral as soon as I end up stopping and rev the engine up to around 1100-1400rpm so the mechanical fan helps it out a bit.
you're halfway onto it, the mech fan and the water pump are both tied to RPMs and when you stop at a light they fall to 500 RPMs which isn't very much. the thermostat also has to respond to increasing temperature, then when you take off the temperature plummets because thermostat is wide open and everything starts pushing again
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  #52  
Old January 1st, 2010, 17:50
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by kastein View Post
Makes me wonder, personally - why not build a radiator with vertical tubes? Results in more tubes in parallel (also shorter so the wasted length at the cool end doesn't come into play.)
The larger end tanks would cost significantly more and use up more of the square inches of frontal area available for cooling fins. While I respect the stated opinions of (some of the) others here, I don't agree that the cooler end of the tube is wasted. It is still shedding BTUs.
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  #53  
Old January 1st, 2010, 17:56
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kastein kastein is offline
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by winterbeater View Post
The larger end tanks would cost significantly more and use up more of the square inches of frontal area available for cooling fins. While I respect the stated opinions of (some of the) others here, I don't agree that the cooler end of the tube is wasted. It is still shedding BTUs.
True. The most efficient heat transfer will occur with the largest temp delta though, I guess it's not so much "wasted" as... not as efficient as the hot end of the tubes. Good point on the tanks, though I tend to think with plastic end tanks it wouldn't be as much of an issue at least - taking up that much more frontal area obviously is still a problem...
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  #54  
Old January 2nd, 2010, 07:22
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Re: XJ Cooling System Deficiencies & Solutions

The XJs cooling system still amazes me. My cooling system is bone stock with factory auzilary trans cooler. Wheeling in over 100* with the AC on for hours on end or driving down the highway at 80mph it never gets anywhere out of the factory range(190-220). While the cooling system is a little odd with the long short radiator its been OK for me.

I have even stayed with the little factory aux trans cooler because it does the job so well. I have pulled a few completly dead jeeps a few miles off some trails and it never gets more than warm(i can reach it through the grille thats broken lol). I figure if I can wheel some decent terrain with a dead jeep in tow and not get the trans even close to hot Its all doing great.
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  #55  
Old January 2nd, 2010, 07:53
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by kastein View Post
True. The most efficient heat transfer will occur with the largest temp delta though, I guess it's not so much "wasted" as... not as efficient as the hot end of the tubes. Good point on the tanks, though I tend to think with plastic end tanks it wouldn't be as much of an issue at least - taking up that much more frontal area obviously is still a problem...
On the issue of plastic tanks (as long as I have 8 years experience in the molding and sealing of them to the core), the bigger they are, the harder they are to mold flat and the harder it is to make them seal (and maintain seal) at least until the warranty expires.
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  #56  
Old January 2nd, 2010, 20:52
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SleeperXJ SleeperXJ is offline
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Re: XJ Cooling System Deficiencies & Solutions

This thread has some good information in it.
I'd like to know how the OP's rig is set up. Tire size, axle gearing etc.
When I first started modding my rig, going from 29" tires to 31 without
re-gearing really played a big roll in increasing engine temps on long climbs.
I have since installed 4.10's and that helped. Increasing vehicle weight with
bumpers, JKS control arms and heavier springs has led to upgrades in my
cooling system which include 3 row radiator, high flow t-stat housing
and high flow water pump (Hesco). I wheel a lot in Death Valley and my rig
would occasionaly get over 220 deg in a slow crawl with AC on. I've found that
running in 4Lo helps keep coolant flow high enough so that I can run my AC again.
My rig is a 99, Auto, AC, np231 T-case, still on 31's until next summer (33's).
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  #57  
Old January 3rd, 2010, 08:49
SuzysJ SuzysJ is offline
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Re: XJ Cooling System Deficiencies & Solutions

. . the shape of the radiator. The styling of the XJ requires a long radiator but with a short height, which limits it's overall capacity to cool

This is not only correct, but common sense correct. Just enough radiator, but it works. There's just no reserve. We've owned three XJ's the past 23 years and never a cooling problem. But I've owned other cars with cooling problems, huge radiators on some of them, and each time it was:

1] poor maintenance & ignoring problems
2] alteration/removal of airflow devices

So here's the rant: I learned the hard way to simply start from scratch, and replace everything, one time. (Timing chain, too). Starting by removing the block plugs/drains and scraping out the crud. Then using PRESTONE Flush -- the long and time-consuming version and THEN flushing out the system with multiple changes of distilled water (fill, run engine at fast idle until thermostat opens and longer; cool, drain, start over. Takes most of two days). And then using ONLY premix with either SCHAEFFERs #258 or RMI-25 per directions.

The "dreaded" 331 head is more likely a result of severe overheating. Only takes once.

I don't know how many threads here and on other JEEP sites where I have read of abuse: ignoring problems until the vehicle becomes inoperable; admitted by the owner. It is so common as to be part of being a Jeeper. Ironically, it's the main testament to the durability of the vehicle. I recommend XJ's all the time, since, "thousands of young guys abuse the #*&% out of them and they still run past 200,000 miles. They're also cheap and easy to fix.

In national surveys going back decades, the cooling system is the most neglected. Read and learn. The Internet has made it so easy compared to decades past.

A replacement radiator is a good idea. But replace EVERYTHING ELSE after painstakingly cleaning out the cooling system.

These JEEP sites are more about "man, that looks cool" and vehicle abuse than they are about proper maintenance. Maintenance is NOT the same as repairs. And the book recommendations go out the window once abuse is regular. I'd say that -- per Ph testing -- that coolant may not be good much more than a year (after above renovation). And I wouldn't keep hoses or fasteners more than three. Etc. Better safe than sorry.

I've put heavier fan clutches on some V8 cars (catalog cross-references) and replaced missing or modded or built fan shrouds. And added dams under radiators that help pull air thru. Upgrade where you can, obviously. The real upgrade would be a coolant filter.

I would NEVER eliminate the in-tank ATF cooler, but do it the way Chrysler has for decades: add one downstream, getting some fan flow [and add an auxiliary filter). That in-tank cooler helps the ATF warm up faster AND reduces temp spikes at slow or low speeds. Quit second-guessing Ph.D. engineers. (And your power steering [PSF] can use a cooler and filter as well [MAGNEFINE, required by Toyota and Ford for AT rebuilds]). The A38 police cruisers were all built this way, as were towing packages.

One can gold plate things all one want, but I'd take low miles junkyard STOCK components any day over fancy aftermarket if the cooling system had not been laboriously cleaned.

I started driving in the early 70's. Muscle cars were cheap (talk about abuse), $1,800 for a V8-454 1970 SS Chevelle was common. Joe Dummy always added a double-pumper HOLLEY, high lift mechanical cam, HOOKER headers, taller, fatter tires and proceeded to grenade the rear end, then the trans, etc. He should have started with the rear axle gearing, then matched the trans (TQ converter) to the cam (which had to work with true compression ratio, etc). Got it backwards in other words.

Same here: lift kit, tall tires, overweight vehicle, etc. Backwards. Gears should have been first . . not, I'll do them later. It only takes one severe overheat to ruin the cooling system.

An automobile is a system of systems. Every change in one system has an effect on every other system.

Last edited by SuzysJ; January 3rd, 2010 at 09:02.
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  #58  
Old January 3rd, 2010, 20:38
BarFlyFisherman BarFlyFisherman is offline
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Re: XJ Cooling System Deficiencies & Solutions

I haven't been around the XJ's for very long...

This is only the 4th XJ that I am building (I guess I should have wised up by now, just shows how stupid I really am).

#1 was a 1984 (V6) wrecked by a drunk driver (burned up), #2 1991 (I6) stolen & recovered stripped, #3 1995 (European "van" 2.5L TD w/5 spd manual) given to oldest son who's still rock climbing & hunting with it, & #4 1999 (I6) is in progress. Only the diesel doesn't have overheating issues.

At work, all of the XJ 4X4's that I had in our fleet had overheating issues (we had 12 in our District alone). All of them had an A/T & A/C. They were diligently maintained on the factory schedule at the dealer!

Every single one of them had issues with overheating, especially when crawling on 4X4 Low with the A/C on.

We attach a 1500 pounds of bumpers, winches, racks, rails, skid plates, aux. gas cans, 2nd battery, etc. Inside we throw another few hundred pounds of gear, not to mention passengers. Then we add lift kits, lockers and change the gearing ratios, beef up the axles, and add larger tires & wheels.

Then we drop the the AT into 1st/2nd gear, drop down into 4X4 low, crank on the A/C, and creep up & down hills in 100F+ heat, and expect the stock cooling system to keep the temperatures down??? Who are you kidding??

Jeep's marketing department promoted the XJ for "casual off-roading" and for "snow covered highways." The XJ was not designed for serious off-roading.

I stand by my earlier statements... that the stock cooling system is adequate for your wife & her trips to Starbuck's.

Before you place all of your faith in the Chrysler PhD Engineers, remember that they are employed by a "FOR PROFIT VENTURE - CHRYSLER" [And if my memory serves me correctly, Chrysler was not very very good at that either (making a profit)!].

The engineers are given design parameters, and and TOLD to design a vehicle that meets those goals "FOR AS CHEAPLY AS POSSIBLE." This means that they are not allowed to include a lot of additional margin for weight hauling or towing capacity, cooling, structural strength, etc. - those all cost money & fuel economy.

This is why we got plastic radiator end tanks, integral transmission coolers (instead of big external ones), marginal gauged wiring harnesses, marginal water pumps, fluid/viscosity fan clutches, low output alternators, minimal skid protection (and it was "wimpy" when offered), 2 row radiators, cheapo thermostats, restrictive exhaust system, and a weak uni-body frame.

It was all about COST.... this is why the Military versions of Jeep vehicles are so sought after. They are built to the buyers specifications, not some executive's bottom line!

Even a properly cared for & well maintained marginally designed cooling system cannot handle the stress we place upon them.

Think about what you've done to your "race engine" that is keeping the temperature down:
larger oil pans
high volume oil pumps
oil coolers
roller rockers, upgraded bearings, pistons & rings (reduced friction - less heat)
installed a header & free flow exhaust
removed your CAT
high flow water pump
hood scoops (increased air flow)
and then you drive at 100mph+ (increased air flow)

Plus a lot of "racers" have stripped a lot of stuff out of their rig: stock dashboard, rear seat, passenger seat, headliner, carpeting, plastic trim, heater/defroster blower, heater core, center console, stereo, rear hatch, spare tire & door glass. Some have even removed the doors!

These rigs run a lot lighter & faster (and therefore cooler) than rock crawlers or hunters loaded with gear.

If these "XJ's" didn't need so much beefing up & work, we'd all be rich(er) and have free weekends to enjoy them in the countryside!

AND you wouldn't be here on the forum!

Last edited by BarFlyFisherman; January 3rd, 2010 at 20:41.
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  #59  
Old January 3rd, 2010, 20:40
BarFlyFisherman BarFlyFisherman is offline
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Re: XJ Cooling System Deficiencies & Solutions

By the way, the 3 core radiator is a lot wider. It adds a 3rd row of the same width to the 2 OEM sized rows.

It is NOT 3 smaller cores jammed into the size of the 1 or 2 core radiator!

Last edited by BarFlyFisherman; January 3rd, 2010 at 20:43.
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  #60  
Old January 3rd, 2010, 20:53
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Re: XJ Cooling System Deficiencies & Solutions

Well, today Goatman pushed his XJ at better than 4,000 RPM's in second gear for about 60 miles with 40" tires and a stock cooling system, and it never got over 200*.. after which he put it in 4 low and sat in a rock canyon revving it hard at what totals out to maybe .125 mph, it still never got over 200*. I was in the passenger seat watching the entire time, I even thought about this thread.

Did I mention its a 4.7 liter stroker and he has a heavy foot?

@barfly, it is 3 smaller cores taking up bigger space. the volume does not go up 100% for each new core.
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