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  #31  
Old December 29th, 2009, 12:29
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by Shorty View Post
are you running the shroud kits for the fans as well?
Yes, you have to run the fan shroud. The radiator is very short and the fan diameter is larger than the radiator, so the fan sticks down below the radiator. The shroud is needed for the best performance.
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  #32  
Old December 29th, 2009, 12:35
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by BarFlyFisherman View Post
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??

Backflush the motor and recheck the radiator. Put the mechanical fan back on, you know, the one you said was no good in your original post, and with a fresh stock clutch fan, the one you said was also no good in your original post. And, make sure you don't have a bad head gasket. A shop can do a chemical test.

You claimed to know so much originally, but now you can't figure it out. Amazing, and typical. This XJ cooling stuff is so simple, and yet people complicate the crap out of it.
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  #33  
Old December 29th, 2009, 13:50
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Re: XJ Cooling System Deficiencies & Solutions

can anyone give me a quick description of how to back flush the motor? I did a cheapo parts store coolant flush before replaceing the radiator, but i still have overheating issues when climbing long hills at freeway speeds any time the outside temp is over 70 degrees.

94, 4.0, automatic and AC. 32x10.5 tires on stock gears. Radiator is a 2 core. tstat is 180, water pump is OEM replacement.
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  #34  
Old December 29th, 2009, 15:16
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Re: XJ Cooling System Deficiencies & Solutions

One thing I noticed in the OP as well is that he says removing the clutch fan will help the water pump pulley - FALSE, the mech fan is on its own pulley, not the water pump. Altho, an electric water pump is a good idea depending on cost.
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  #35  
Old December 29th, 2009, 21:24
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Re: XJ Cooling System Deficiencies & Solutions

I'm not sure what is meant by backflushing either, but I had an overheating problem last summer. Changed out waterpump, t-stat, fan clutch, rad. cap...nothing worked. Then I burped the radiator and problem solved: Remove radiator cap (assuming open cooling system), turn on engine, watch for bubbles. For the first 30 to 45 minutes I just got a steady stream of tiny bubbles and then I got a sudden 3 inch drop in my fluid level...problem fixed, no more overheating. Call it vapor lock, gas bubble, trapped air, or whatever...the fix is easy and dirt cheap. Not sure its so easy with a closed system however. It might help to point the vehicle uphill to facilitate movement of trapped air toward the radiator.

Last edited by Rod Knee; December 29th, 2009 at 21:29.
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  #36  
Old December 29th, 2009, 21:26
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by Rod Knee View Post
I'm not sure what backflushing is either, but I had an overheating problem last summer. Changed out waterpump, t-stat, fan clutch, rad. cap...nothing worked. Then I burped the radiator and problem solved: Remove radiator cap (assuming open cooling system), turn on engine, watch for bubbles. For the first 30 to 45 minutes I just got a steady stream of tiny bubbles and then I got a sudden 3 inch drop in my fluid level...problem fixed, no more overheating. Call it vapor lock, gas bubble, trapped air, or whatever...the fix is easy and dirt cheap. Not sure its so easy with a closed system however.

Another way to help get air out of the system is pull the sending unit for your temp gauge, which is at the rear of the head on the drivers side.. remove it and let any air escape.
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  #37  
Old December 29th, 2009, 21:35
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Re: XJ Cooling System Deficiencies & Solutions

I forgot to mention that I had put in a new 3 core csf radiator 6 months prior to problem. so I knew the radiator wasn't the problem.
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  #38  
Old December 30th, 2009, 08:56
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Re: XJ Cooling System Deficiencies & Solutions

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.
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  #39  
Old December 30th, 2009, 12:27
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Re: XJ Cooling System Deficiencies & Solutions

Quote:
Originally Posted by Rod Knee View Post
I'm not sure what is meant by backflushing either, but I had an overheating problem last summer. Changed out waterpump, t-stat, fan clutch, rad. cap...nothing worked. Then I burped the radiator and problem solved: Remove radiator cap (assuming open cooling system), turn on engine, watch for bubbles. For the first 30 to 45 minutes I just got a steady stream of tiny bubbles and then I got a sudden 3 inch drop in my fluid level...problem fixed, no more overheating. Call it vapor lock, gas bubble, trapped air, or whatever...the fix is easy and dirt cheap. Not sure its so easy with a closed system however. It might help to point the vehicle uphill to facilitate movement of trapped air toward the radiator.


Yeah, anytime coolent is let out, like changing a radiator or water pump, it's possible to get air trapped in the block and it will always overheat. Parking uphill helps, and running it a little then re-burping it.

Backflushing is sticking a garden hose in the radiator hose and running water through the system backwards from it's normal flow. You can get a flush kit, or chemicals, put the stuff in and let the engine idle for awhile and then backflush the system. Should always be done when a radiator is replaced.



Quote:
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.
Good comment, I wonder how much difference it makes. I know a lot of us who have lifts and bigger tires also have bigger tranny coolers, and many bypass the radiator. I know I bypass the radiator.
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  #40  
Old December 31st, 2009, 20:40
BarFlyFisherman BarFlyFisherman is offline
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Re: XJ Cooling System Deficiencies & Solutions

Goatman - You don't need to be a condenscending d!kh#@d. We'd all be better if you shared your vast years of wasted time, experience, and worthless knowledge, instead of passing judgement on us clueless idiots who needlessly pad the pockets of the aftermarket auto parts manufacturers. Words to remember - a sniper doesn't give away his presence until he fires!

The OEM cooling system still sucks, regardless of the problems that I'm individually having. You say that the OEM cooling system is great... then blab on about how the radiator is the wrong shape, airflow insufficient, blah, blah, blah... Which side of your face are you going to talk out of next?

I did "back flush" the cooling system. I installed a garden hose flushing T in the heater hose & ran & drained the system 2 times, on 2 occasions (2 x 2 = 4). An application of Prestone Cooling System Flush each time (or maybe you didn't bother to read the entire thread).

I didn't do the radiator "burp." Makes sense, as even babies burp after a good meal! I did observe that the fluid level inside of the fluid reservoir was going down... that could explain it! I'll try that I report back if I get any air belching out. Next is the head gaskets - I know a torn gasket is SO readily visible on a casual inspection (how could I have missed seeing it?).

Last edited by BarFlyFisherman; December 31st, 2009 at 20:44.
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  #41  
Old December 31st, 2009, 20:53
BarFlyFisherman BarFlyFisherman is offline
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Re: XJ Cooling System Deficiencies & Solutions

I have heated my engine up with the A/C on & scanned the engine block with an IR camera/sensor. I would expect that a blocked passage or water jacket would result in a "hot spot." I crawled all over it & under it with the sensor, but I found none.... any other CONSTRUCTIVE ideas or suggestions out there?

Don't beat me up - I get that at home, but I put up with it because there are fringe benefits!
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  #42  
Old December 31st, 2009, 23:38
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Re: XJ Cooling System Deficiencies & Solutions

You can rag on me and make fun of me all you want, but it doesn't change the fact that you came on this forum and posted a fairly in depth expose on the XJ's inadequate cooling system with your own list of fixes. You acted and spoke like an expert, and yet most everyone who has posted on this thread has disagreed with your info and conclusions. Other than your posts, this thread has been pretty darn informative if anyone is chasing overheating issues.

Don't misquote me. I said the XJ cooling system works just fine when everything is in proper working order, but it doesn't have a lot of reserve cooling capacity when something in the system has deteriorated performance. That's different from what you said, which is that the XJ cooling system is inadequate from the get go. Based on your analysis, every XJ out there should be having cooling problems, especially if you wheel it at slow speeds. Hmmmm........a whole bunch of people are doing just that with no problems.

First you come on here acting like an expert, then you start begging for help. I answer with sarcasm, which I happen to think is justified, and you take it personally and lash out. Oh well, I hope you get your cooling problems figured out. Let us know when you get that head gasket checked.
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  #43  
Old January 1st, 2010, 00:05
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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. We'd all be better if you shared your vast years of wasted time, experience, and worthless knowledge, instead of passing judgement on us clueless idiots who needlessly pad the pockets of the aftermarket auto parts manufacturers. Words to remember - a sniper doesn't give away his presence until he fires!
Congratulations, you just made the first nomination of 2010.

(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.)
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  #44  
Old January 1st, 2010, 09:19
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Re: XJ Cooling System Deficiencies & Solutions

If you guys want to argue the pros/cons of hooking up the aux. exterior transmission cooler in series with the tran. cooler in the radiator vs doing a bypass, I'm willing to sit and listen. Lets say, running a 3 core csf radiator (which is what I have), if that makes any difference.
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  #45  
Old January 1st, 2010, 11:56
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Re: XJ Cooling System Deficiencies & Solutions

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Originally Posted by Rod Knee View Post
If you guys want to argue the pros/cons of hooking up the aux. exterior transmission cooler in series with the tran. cooler in the radiator vs doing a bypass, I'm willing to sit and listen. Lets say, running a 3 core csf radiator (which is what I have), if that makes any difference.

i have never lived up north where it gets cold.....but in florida most people with modified(keyword here is modified) rigs will eliminate the "cooler" in the radiator and runan exterior cooler. the radiator cooler will heat up the trans fluid to normal operating temps and keep it at that temperature, which is good up north in the cold.

i personally eliminated the cooler inside the radiator and replaced it with a nice B&M stacked cooler and my tranny temps are always below 220* on my gauge.
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