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Improving the cooling on our TJs

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TexasTJ2004

I love my TJ
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I had more rust than this

C300AD78-7D56-4B6F-AF97-A45E778AAAEC.jpeg
 

Derek Thompson

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Aug 3, 2022
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I bought the AutoZone radiator before I joined the forum. I know, excuses, but I have a valid one.

I too bought an autozone radiator. replaced it 3 time in a year and a half. When it fails again or I have a hint of a overheating problem a mopar radiator will replace it. Never again will I cheap out on my jeep with such an important part
 
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TexasTJ2004

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I too bought an autozone radiator. replaced it 3 time in a year and a half. When it fails again or I have a hint of a overheating problem a mopar radiator will replace it. Never again will I cheap out on my jeep with such an important part

How exactly did it fail? Leaks or was not cooling well?
 

Lifted straight six

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Oct 26, 2020
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arizona
For some reason I thought that it should never go beyond 210F and that it will blow up in a minute.
How do you identify potential overheat then? Is it when the temperature goes further from 210F?

I have gone through several cooling issues here in Arizona, the advice I can offer you, that I got from these forums(which has worked extremely) is… water pump and radiator need to be mopar, and mopar only, do a nice 195 degree thermostat(mopar or stant) personally I run mopar and have had no issues, constant tension clamps, use only 50/50 antifreeze, and get an extreme duty fan clutch for a climate that gets as hot as places like AZ, Texas, Socal, etc. I run in 110 degree weather almost every single day, and only time my temp reads over 210 is sitting in a drive thru, or at highway speeds, and even then I have only personally seen it hit 219(which is completely normal). They say rule of thumb for temperatures in extreme climates is 210-230, if you aren’t over 230 constantly, and inbetween 210-220 most of the time, don’t stress.
 
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TexasTJ2004

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I finished my flushes, canceled the heater core, replaced thermostat and fan clutch, and based on my today's 4 hours of driving in Houston heat and humidy with 97F, the only times when it crosses the 210F (reaches ~225F)is when I am in drivethrough with ice cold AC. In all other situations, it is ~210F. On Highway, it is slightly under 210F. This is AC blowing 45F cold air, which is impressive.
I would say that my cooling issues are much less of a problem now.
The difference between Arizona and Houston is in Humidity, which has severe impact on AC. The moment that AC is on, AC emits much more heat in Houston, and I believe that the difference is significant.
With AC off, I would not cross 210 i believe.
 
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freedom_in_4low

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I finished my flushes, canceled the heater core, replaced thermostat and fan clutch, and based on my today's 4 hours of driving in Houston heat and humidy with 97F, the only times when it crosses the 210F (reaches ~225F)is when I am in drivethrough with ice cold AC. In all other situations, it is ~210F. On Highway, it is slightly under 210F. This is AC blowing 45F cold air, which is impressive.
I would say that my cooling issues are much less of a problem now.
The difference between Arizona and Houston is in Humidity, which has severe impact on AC. The moment that AC is on, AC emits much more heat in Houston, and I believe that the difference is significant.
With AC off, I would not cross 210 i believe.

Mine runs about the same as yours at idle (takes about 20 minutes but will stabilize in the 220s) but it'll also get to ~220 on the highway, with AC on. And likewise, without AC I'm not sure it would ever pass 210.

It's confusing because my 99 TJ with fresh fan clutch, Mopar radiator and water pump never passed 210 except for momentary spikes along with a major load change (abruptly going from highway speed to full stop/idling), even when it was 95-100. I know the humidity thing works in theory, but since I switched to the 2006 LJ and moved to Oklahoma before experiencing a summer up there, there are too many variables for me to know whether I can squarely blame the humidity or whether there's something different about the rig.
 
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TexasTJ2004

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Mine runs about the same as yours at idle (takes about 20 minutes but will stabilize in the 220s) but it'll also get to ~220 on the highway, with AC on. And likewise, without AC I'm not sure it would ever pass 210.

It's confusing because my 99 TJ with fresh fan clutch, Mopar radiator and water pump never passed 210 except for momentary spikes along with a major load change (abruptly going from highway speed to full stop/idling), even when it was 95-100. I know the humidity thing works in theory, but since I switched to the 2006 LJ and moved to Oklahoma before experiencing a summer up there, there are too many variables for me to know whether I can squarely blame the humidity or whether there's something different about the rig.

Any chance that you have airflow differences between these 2? Like the old TJ didnt have the Winch in the front and new one has it?
From my Israeli experience, their (Israeli military deploying TJ in masses) instructions for TJs were forbidding to install anything that anyhow reduces the airflow.
I am running a big ass Warn Zeom Platinum 8000 winch, which significantly impacts the airflow.
Also, I have automatic, which the oil is reaching let's say 220, will add more heat to the system. I havent installed yet the Derale cooler for my 42RLE, so it could be better after it.
Also, from my reserach into the general cooling designs w/o electric fans - they are designed for variance in coolant temperature, because w/o thermostatically controlled electric fan it is all not such a precise science.
I will still plan for adding small electric auxilary radiator (small heater core from YJ and 6 inch electric fan), that will be located in the back under the tub and will get the hot the coolant from the heater core line, and will help to keep the temperature in ~210 range even when standing in traffic jam or at school pickup line with AC blasting at 42F when outside is 100+F
 

freedom_in_4low

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Any chance that you have airflow differences between these 2? Like the old TJ didnt have the Winch in the front and new one has it?
From my Israeli experience, their (Israeli military deploying TJ in masses) instructions for TJs were forbidding to install anything that anyhow reduces the airflow.
I am running a big ass Warn Zeom Platinum 8000 winch, which significantly impacts the airflow.
Also, I have automatic, which the oil is reaching let's say 220, will add more heat to the system. I havent installed yet the Derale cooler for my 42RLE, so it could be better after it.
Also, from my reserach into the general cooling designs w/o electric fans - they are designed for variance in coolant temperature, because w/o thermostatically controlled electric fan it is all not such a precise science.
I will still plan for adding small electric auxilary radiator (small heater core from YJ and 6 inch electric fan), that will be located in the back under the tub and will get the hot the coolant from the heater core line, and will help to keep the temperature in ~210 range even when standing in traffic jam or at school pickup line with AC blasting at 42F when outside is 100+F

same winch and front bumper. Only difference is this one has a body lift and the previous one didn't...which would raise 1.25" of the radiator out from behind the winch. I've lit up the engine compartment and looked through the condenser and radiator to make sure there's no mud or anything blocking the fins.
 

Ericshere03

TJ Enthusiast
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Apr 8, 2019
Messages
205
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Feenicks
I have gone through several cooling issues here in Arizona, the advice I can offer you, that I got from these forums(which has worked extremely) is… water pump and radiator need to be mopar, and mopar only, do a nice 195 degree thermostat(mopar or stant) personally I run mopar and have had no issues, constant tension clamps, use only 50/50 antifreeze, and get an extreme duty fan clutch for a climate that gets as hot as places like AZ, Texas, Socal, etc. I run in 110 degree weather almost every single day, and only time my temp reads over 210 is sitting in a drive thru, or at highway speeds, and even then I have only personally seen it hit 219(which is completely normal). They say rule of thumb for temperatures in extreme climates is 210-230, if you aren’t over 230 constantly, and inbetween 210-220 most of the time, don’t stress.

As a zonie, I agree. However I’d ad that a ZJ V8 fan clutch as another upgrade. In Hayden terms it’s a severe duty which spins slower when cold and faster when hot plus supposed to last longer … Ive used this one once and it can HOWL but coolant temps plummet. But Mopar pump and radiator are a sure way to avoid all issues. I’ve had success with a Oreilly radiator in AZ with all else stock, this was years ago. More currently I’ve bought 2 Jeeps that had aftermarket radiators that ran hot, but only with AC.
 

xXDavidCXx

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Jun 17, 2021
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113
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AZ
You are screwed. Sorry:). Head gasket or the head itself in the worst case.

Well....I flushed out the thermocure and put in prestone stuff, then I tested for an exhaust leak again.

This time I pumped more slowly and was more diligent in keeping the fluid out of the tester.

Passed.

I think I bit off on bubbles from incomplete burping and fluid ingestion from being too quick with the pump.


Now, what about the attached video showing a possible crack in the block under the oil cap?

My last oil change analysis mentioned the possibility of coolant in the oil.
 
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TexasTJ2004

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Your theory is that a mix of thermocure and distilled water would cause the tester fluid to become yellow? This would an interesting experiment. I would try to mix thermocure, water and tester fluid just to check the theory.
 

Dggall

New Member
Joined
Dec 23, 2021
Messages
13
Location
Arizona
Sharing: Mopar radiator, Mopar water pump, "Stant" thermostat and Hayden 2771. Job complete.

Dare I say successfully completed with only a few miles on the LJ for op checking the temp and for leaks. I put the 2005 auto Mopar rad in my 2004 auto LJ using the QD trans line adapters recommended earlier in this thread. Didn't see a lot of alternatives to that and checked local parts stores and Ace for any other options (nil). I'll keep a close eye on those as the Amazon ratings were not great with complaints about leaks.

Some discussion on this forum about thermostats being all Motorad....I ordered the Stant Superstat from Summit Racing and a Motorad showed up. Not sure we have a choice on that anymore.

One thing I ran into is with the reuse of the hardware. The old water pump fan pulley bolts were not compatible with the Mopar water pump. My water pump was replaced by a PO with some aftermarket (couldn't tell what brand) and those 4ea bolts were 5/16-24 but the Mopar water pump requires 5/16-18. A trip to Ace Hardware solved the problem without issue. It did require an unplanned parts run though, so be aware of that based on your situation.

Thanks again to everyone that contributed to this thread. Not sure I could have got this job completed the same or as quickly without it.

Cheers,
Dave
 
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TexasTJ2004

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Neither did mine. But it definitely wasn't not sufficient. Switch to a Koyorad and my temps are much better. No more idle temp creeps

So you had a working setup with temperature creeping in idle and you replaced it with Koyorad and it works better for you now?
 

LittleTankTJ

TJ Euthanist
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Joined
May 9, 2019
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566
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Bay Area, CA
So you had a working setup with temperature creeping in idle and you replaced it with Koyorad and it works better for you now?

Yup. The pump and thermostat had been replaced as well as the fan clutch.

The AutoZone rad was fine except in high-heat+ac or high-heat plus idle.

It never failed but I finally decided it was the weak link and that was correct