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  #16  
Old September 27th, 2009, 11:31
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ehall ehall is offline
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Re: XJ Cooling System Deficiencies & Solutions

The cooling system seems to work just fine when it is maintained properly (which includes proper fluids). My highway temps are 195 and idle temps are 215, no matter what the outside temperature is, which tells me that the thermostat and radiator correctly transfer heat out of the engine according to the internal temperature.

I agree that taking them offroad opens them up to heat transfer problems that they were not really designed for. IE, high torque at low RPMs is definitely a recipe for heat buildup. There are things you can do to help the system along here, like spacing the hood to help evacuate heat, or using electric fans to help evacuate heat (wont do anything if coolant isn't flowing), or an electric water pump to maintain constant coolant pressure. You could probably draw a quadrant of engine speed vs engine load and these kinds of uses are going to be outside the designed scope. So is drag racing though, or hauling heavy loads, or doing any number of other things that are in weird corners
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  #17  
Old September 27th, 2009, 11:56
joe_peters joe_peters is offline
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Re: XJ Cooling System Deficiencies & Solutions

Quote:
Originally Posted by fasteddieyj View Post
118mph in an XJ? Your a braver man than I am.
Maybe he meant 118kph?

I think the stock cooling system is adequate for what the Jeep engineers designed it for--grocery getter, winter driving in 4hi, minimal use of 4lo.

Best XJ for cooling from the factory: manual trans, no a/c.

Worst XJ for cooling from the factory: auto trans, a/c.

And then we come along. Rock crawlers, sand dogs, mud hogs, and generally people with a modicum of common sense, but with an overriding urge to go places that give us a little bit of a "pucker factor".

We like bigger bumpers, bigger wheels and tires, winches. We like to put p/s and trans coolers in front of the radiator.

Does a lift alone make a difference in cooling? I don't know. Does the height of the vehicle change the air flow through the radiator? I don't think it would, unless a lift, in conjunction with the removal of the "splash guard", contributes to air turbulence in the engine compartment.

Increasing the efficient air flow through the radiator is in my opinion the answer to cooling issues, if all parts are the system are in proper working condition.

I believe a ZJ fan clutch upgrade is dollar-for-dollar the best first upgrade to the cooling system. At $44 and 30 minutes of sweat, it can't be beat.

I have been thinking of making a radiator "scoop". Thinking along the lines of four pieces of aluminum cut for the area behind the grill that can be screwed into place to concentrate the airflow through the radiator.

I am also going to replace the trashed "splash guard" with an OEM front skid plate.

However, as I have ZERO overheating issues (manual trans, ZJ fan clutch), both the radiator scoop and front skid are low priorities for me at this time.
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  #18  
Old September 27th, 2009, 13:45
Lodi Jim Lodi Jim is offline
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Re: XJ Cooling System Deficiencies & Solutions

Good information in this thread.
It appears that my 300k mile Renix with 180 T-stat, radiator from a '95,
manual switch for electric fan, and running a manual transmission (with A/C)
is the best combination to keep temps down and Calif. smog nazis happy.
I wheel with the heater on low and temp. turned down. I turn on the electric fan when temps get close to 200'F. I am running 35's and 5" lift. I have had my XJ for 14 years. I wheel in the rocks of Rubicon, Fordyce, Dusy, Barrett,etc.
Only issues I have had was before changing to poly motor mounts,and fan contacting the radiator. Also put stress cracks in the plastic side tanks before stiffening up the frontend.
It appears that manual transmission, Renix era XJ's like preventive maintenance to the cooling system.
It appears that the automatic transmission crowd needs to address the tranny cooling with auxillary coolers and switches to have torque converter lock-up. Those of you that want to get fancy, you could put a tranny temp gauge and have an e-fan for the cooler.
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  #19  
Old September 27th, 2009, 16:47
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Pharaoh XJ Pharaoh XJ is offline
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Re: XJ Cooling System Deficiencies & Solutions

Quote:
Originally Posted by joe_peters View Post
Maybe he meant 118kph?

I think the stock cooling system is adequate for what the Jeep engineers designed it for--grocery getter, winter driving in 4hi, minimal use of 4lo.

Best XJ for cooling from the factory: manual trans, no a/c.

Worst XJ for cooling from the factory: auto trans, a/c.

And then we come along. Rock crawlers, sand dogs, mud hogs, and generally people with a modicum of common sense, but with an overriding urge to go places that give us a little bit of a "pucker factor".

We like bigger bumpers, bigger wheels and tires, winches. We like to put p/s and trans coolers in front of the radiator.

Does a lift alone make a difference in cooling? I don't know. Does the height of the vehicle change the air flow through the radiator? I don't think it would, unless a lift, in conjunction with the removal of the "splash guard", contributes to air turbulence in the engine compartment.

Increasing the efficient air flow through the radiator is in my opinion the answer to cooling issues, if all parts are the system are in proper working condition.

I believe a ZJ fan clutch upgrade is dollar-for-dollar the best first upgrade to the cooling system. At $44 and 30 minutes of sweat, it can't be beat.

I have been thinking of making a radiator "scoop". Thinking along the lines of four pieces of aluminum cut for the area behind the grill that can be screwed into place to concentrate the airflow through the radiator.

I am also going to replace the trashed "splash guard" with an OEM front skid plate.

However, as I have ZERO overheating issues (manual trans, ZJ fan clutch), both the radiator scoop and front skid are low priorities for me at this time.
no that was 190 kph (last friday) this is the point when i started to think about the things that can go wrong, after all its at stock height with 235s.

Regarding the fan clutch I used the old one to mess with it, I tried adjusting the spring/coil and was better than bolting the fan to the pulley because at heigh revs 4k + the clutch starts to slip avoiding the fan to...... you know.

But I drove it all last summer with fan bolted & redlined it alot but was not so happy about it.

any body knows how I can bypass the heater core & ensuring that all water goes through the radiator, cause a simple bypass will blow hot water back into the block ?
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  #20  
Old September 27th, 2009, 18:30
def.ho def.ho is offline
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Re: XJ Cooling System Deficiencies & Solutions

i overheated today driving from Redding CA up to yreka. mostly my fault pushing 75-80mph at around 3000rpm up the mountain. it was about 100 degrees in my defense though :P
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  #21  
Old September 27th, 2009, 18:47
nelson7172 nelson7172 is offline
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Re: XJ Cooling System Deficiencies & Solutions

A restricted exhaust system can also cause overheating.
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  #22  
Old December 28th, 2009, 18:23
BarFlyFisherman BarFlyFisherman is offline
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Re: XJ Cooling System Deficiencies & Solutions

The 3 row radiator fit SMOOTHLY WITHOUT any trimming! Since I had to disconnect the transmission cooler, I decided to add a auxiliary transmission cooler in front of the radiator (& behind the grill).

Everything has run great for months... recently I was traveling at 60 MPH up a steep hill, outdoor temp was 60F, & had the defroster on (means that the A/C was on), and it again spiked to 265F.

I turned off the defroster & turned on the heater to bring the temperature back down. It worked quickly...

This is what I have done so far to the cooling system:

High flow Mr. Gasket thermostat (stock temp)
High flow thermostat housing
Hi-Flow water pump
3 row aluminum radiator
New radiator cap
New upper & lower hoses
(3) electric fans with adjustable thermostat relay (set at 190F)
Added a hood air scoop (facing in reverse to create a negative pressure area in the engine compartment to increase air flow)
4 complete system flushes
New Heater Hoses
50/50 coolant

The electric fans are wired into the automatic relay, so that they are forced to come on with the A/C.

I have about 1000 lbs of gear on/in my 1999 XJ 4.0L A/T 4x4 (safari rack, after market bumpers, winch, rock sliders, a dead boar in cargo area, mother-in-law on roof, etc). The drivetrain is stock, OEM tires/wheels, w/a 3" lift. Lowered transfer case with SYE & new driveshaft.

Can anyone come up with a reason why this thing is still overheating??

Last edited by BarFlyFisherman; December 28th, 2009 at 18:30.
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  #23  
Old December 28th, 2009, 18:28
BarFlyFisherman BarFlyFisherman is offline
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Re: XJ Cooling System Deficiencies & Solutions

I have a completely new exhaust system connected to the stock manifold. It is the stock diameter, new CAT & muffler to the tail pipe... It is less than 4 months old & there is no damage to it.

So that can't be it.
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  #24  
Old December 28th, 2009, 19:09
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bj-666 bj-666 is offline
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Re: XJ Cooling System Deficiencies & Solutions

if any of you are up for some real reading and excellent tech read the tech article on pirate4x4 pertaining to cooling systems. there is a lot of miss information floating around that leads to a lot of wasted money on issues that don't exist.
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  #25  
Old December 28th, 2009, 19:23
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hubs97xj hubs97xj is offline
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Re: XJ Cooling System Deficiencies & Solutions

Blown head gasket/cracked head?
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  #26  
Old December 28th, 2009, 23:39
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Goatman Goatman is offline
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Re: XJ Cooling System Deficiencies & Solutions

The initial post in this thread is bullshit. It has been proven over and over again that an XJ cooling system in good working order works just fine, even with lifts and bigger tires. However, the original stock single core radiator eventually needs to be replaced with a larger double or triple core radiator.

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.

For this reason, the XJ cooling system doesn't have a lot of reserve cooling capacity, so if there is any part that begins to have a problem there can be overheating. If the cooling system is in good condition, it will cool just fine. Many of us have strokers, which put out more power and more heat, and with a good higher capacity replacement radiator along with all other parts being stock there are no heating problems. I race mine, with a stroker, and the only part of my system that isn't stock is the radiator, which is a multi-core replacement radiator, and it's never overheated while pre-running or racing.......and that's pushing soft comp compound 40" tires with low air pressure, so it's quite a load on the motor.

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. I've also seen, and experienced, a new radiator become partially plugged after a year or two because the engine didn't get backflushed when the new radiator was installed, and crud from the engine partially plugs the newer radiator.
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  #27  
Old December 29th, 2009, 05:33
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Re: XJ Cooling System Deficiencies & Solutions

are you running the shroud kits for the fans as well?
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  #28  
Old December 29th, 2009, 06:20
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jdougn jdougn is offline
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Re: XJ Cooling System Deficiencies & Solutions

Quote:
Originally Posted by BarFlyFisherman View Post
I have a completely new exhaust system connected to the stock manifold. It is the stock diameter, new CAT & muffler to the tail pipe... It is less than 4 months old & there is no damage to it.

So that can't be it.
Is it something other than the cooling system then? Perhaps the engine is not running correctly and causing an overheat?
BTW, good article and since many XJs do experience overheating, an important article. My '98 still runs a bit hot in the summertime at highway speeds and if/when offroad rock crawling. Setup is Auto, 4.0, 33x12.5 ATs, 4.56 gearing, 5"(+-) lift. I guess I'm just too used to my Chevy work van running at 195 degrees regardless of external conditions. My mechanic points out that for starters an XJ is significantly larger and heavier than a Wrangler so that alone puts added stress on the cooling system.
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  #29  
Old December 29th, 2009, 10:54
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QuillsXJ QuillsXJ is offline
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Re: XJ Cooling System Deficiencies & Solutions

I run my 4.0 XJ with most of the A/C system and the condenser removed and I have the mechanical fan removed as well. I took the auxiliary electric fan and hard wired it to an on/off fulltime ignition switch in the cab. I have a new radiator, coolant, hoses and t-stat and I have not had anywhere close to a problem...yet. Granted I do live in northern Washington state where we are lucky if we see maybe a couple days a year in the 90's. I run 33" tires, stock gears, 7" lift, and have an auto trans.

Last edited by QuillsXJ; December 29th, 2009 at 11:27.
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  #30  
Old December 29th, 2009, 11:31
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Re: XJ Cooling System Deficiencies & Solutions

This thread is so full of fail.

You'll find a trend in all of these XJ forums all over the world. Someone has cooling problems. They upgrade to a gimmick radiator and still have cooling problems. Then comes the high flow water pump, followed by bigger fan clutch or electric fans, upgraded thermostat .. and they still have cooling problems.

Eventually they flush the block and or fix their blown head gasket and it runs cool.

Every damn time.
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