3/4 overheat

chereveco · **Posted:** Sun Apr 23, 2017 7:13 pm

Today is the second time...

I was driving the KK uphill, behind some truck, narrow and windy road.

Then I noticed that the temperature started to rise, and it went all the way to 3/4.

Last year it happened for the first time, in same driving conditions.

So replaced the OEM thermostat for one of those Fail Safe that rockauto.com sell's and states are way better than OEM. Also new radiator cap. ( Old thermostat was bad by the way ).

Today temp raised again, no coolant leaks, level in expansion tank is normal and hot.

What could it be.?

Note: with the old KJ 2001 did the same driving several times. Never a single issue regarding raising temperature.

Regards,

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tjkj2002 · **Posted:** Sun Apr 23, 2017 8:11 pm

1st get that failsafe t-stat out ASAP,they always fail within weeks of install.Never seen one last more then a month.OEM is the only proven t-stat that works in the 3.7.

Need more info like..................

-last coolant flush? if so what coolant used?
-standard cooling or HD cooling?
-any aftermarket stuff(lights,bumper,winch,and such) hanging on the front?
-OE air darn still in place?
-AC on?

Since driving behind a truck at low speeds you got reduced airflow and most likely in "D" thus constantly hunting for gears and maybe the AC on,all which create massive heat soak which the stand alone trans cooler that is part of the AC condenser can't handle heat loads like that which in turns makes the radiator basically do nothing.

Added weight from skids,larger tires,and all that adds to the problem and block proper airflow also.

Oh and the '02 KJ(no such thing as a '01 KJ) had the 45RFE truck trans and a in-radiator trans cooler that can deal with high heat soak conditions better then the setup in any KJ/KK with the 42RLE trans.

chereveco · **Posted:** Sun Apr 23, 2017 9:02 pm

Thanks for your help.

1- I'll buy the OEM thermostat this week.
2- At 125k miles, actually is 127700, used Toyota's OEM coolant. Their dealer is closer, and since no antifreeze is required down here, just bought it.
3- Just a LED bar under the bumper. First time that happened nothing were installed in the front end.
4- Original air box with K&N air filter.
5- A/C on on both times, driving with full day light, two people on board.
6- Before this 2008 it was a 2001 XJ ( sorry for the typo ), with AW4 tranny.

Pics of both:

P.D.
Notice that the KJ rims mounted on the XJ now are riding on the KK... And it Looks way better..

Thanks again...

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lfhoward · **Posted:** Sun Apr 23, 2017 9:18 pm

Part of your overheating issue might be that the Toyota coolant isn't playing well with the OEM coolant. These Jeeps require HOAT coolant, which can be Mopar or Zerex G05. Universal coolant or Dexcool or anything else will react chemically with the HOAT/ coolant passages and form a clumpy mess that can clog your heater core and radiator and cause engine cooling problems. I would recommend flushing your cooling system out ASAP before things go bad with that Toyota coolant (unless they use HOAT too). How long has it been in?

PS. The KJ wheels look nice on the KK!

chereveco · **Posted:** Sun Apr 23, 2017 9:25 pm

Ok, I'm going with you,

The Toyota coolant has been circulating for around 2000 miles, since I changed the water pump.

I'll pay a visit to the local Jeep dealer, to get some HOAT Mopar coolant and a thermostat...

Last year's overheating was with pretty old OEM thermostat and OEM coolant supposedly....

Then I'll go for a test drive in the same mountain road that overheated the car the first time, ( only twise in a hole year, normal city hwy driving temperature is at normal level: 1/2 ).

Once the slow moving truck gets over passed, and speed regains on flat or down hill; temp cools down very easily, until next slow traffic or heavy and or windy up hill gets encounter, and so on... Temp keeps moving up and down ( slowly ), until I get off the mountain...
Regards

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tjkj2002 · **Posted:** Sun Apr 23, 2017 9:26 pm

Yep that toyota coolant is not the correct coolant.Buy the correct HOAT coolant(Ford,MOPAR,or Zerex GO5) and mix 50/50 with distilled water.Just be aware that MOPAR switched to OAT coolant(AKA dexcool) for '13+ models so if you go there get the correct HOAT coolant.Even if it never get's below 80 degrees or so you still need a 50/50 mix of coolant/distilled water as coolant increases boiling point as well as having freeze protection.

Long and steep grades at low speeds should be done with OD locked out and if steep enough place trans in 2nd gear and turn off the AC.Yeah it sucks with the AC off but AC adds alot of undue heat stress on the cooling system.

chereveco · **Posted:** Sun Apr 23, 2017 10:05 pm

tjkj2002 wrote:

Yep that toyota coolant is not the correct coolant.Buy the correct HOAT coolant(Ford,MOPAR,or Zerex GO5) and mix 50/50 with distilled water.Just be aware that MOPAR switched to OAT coolant(AKA dexcool) for '13+ models so if you go there get the correct HOAT coolant.Even if it never get's below 80 degrees or so you still need a 50/50 mix of coolant/distilled water as coolant increases boiling point as well as having freeze protection.

Long and steep grades at low speeds should be done with OD locked out and if steep enough place trans in 2nd gear and turn off the AC.Yeah it sucks with the AC off but AC adds alot of undue heat stress on the cooling system.

I don't have OD switch on my tranny...

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GordnadoCRD · **Posted:** Sun Apr 23, 2017 10:47 pm

no lockout button on the shifter?

chereveco · **Posted:** Sun Apr 23, 2017 11:37 pm

Haven't seen a late Jeep or KK bearing it...

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MarkZ28 · **Posted:** Mon Apr 24, 2017 2:15 am

Dexcool is crap. It clumps up and plugs heater cores. Worked in a GM dealership. Lots of warranty work on the newer GM trucks with plugged up heater cores die to GM dexcool coolant.. I hate that crap, any vehicle I get gets flushed out if its dexcool and the old green coolant is put back in. Never had an overheating oroblem or any other problem runningvit in the Liberty or any other vehicle.

Scar0 · **Posted:** Mon Apr 24, 2017 4:04 am

chereveco wrote:

I don't have OD switch on my tranny...

chereveco wrote:

Haven't seen a late Jeep or KK bearing it...

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Unless you have a manual trany or a CRD (diesel engine with the NAG1 Trany) there should be one by the shifter. It says Tow/Haul on it.
Here is a pic of it from At The Helm.
Just forward of the "P(park)" Right center of the Pic.

Push is once and it locks out OD, push it again to turn OD back on.

chereveco · **Posted:** Mon Apr 24, 2017 11:24 am

LoL, thanks for putting me out of my ignorance....

In all these years never towed anything... and never wondered out that button being OD as it is for example in my 2002 Camry that is located in the shift lever...

How does it work?

P.D. I'll buy the thermostat tomorrow all together with the coolant HOAT and destilled water...

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chereveco · **Posted:** Mon Apr 24, 2017 1:30 pm

It, seems that the local Jeep dealer is out of that coolant HOAT.

Mine is 2008 KK 3.7.

Toyota says it's ok with their coolant, it meets that spec.

I'll keep on that one...

As I read above, mine doesn't need HOAT...

Toyota coolant has been circulating in the KK's system for some time already, and still is crystaline clear... No sludge, nor color change...

Been investigating a little bit on this.

Hope that new thermostat will solve my issue....

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lfhoward · **Posted:** Mon Apr 24, 2017 2:21 pm

Interesting. Maybe if they flushed every last trace of the original HOAT out of your system you could be ok. I know that HOAT and Dexcool do not mix together with good results.

In terms of the Tow/Haul button, when depressed it changes the shift points slightly (delaying upshift) and prevents the transmission from going into overdrive (4th gear). This will keep the transmission cooler and happier in situations where you are carrying heavy loads or going up steep hills where it would otherwise shift back and forth a lot between 4-2-3-4 etc. When Tow/Haul is engaged, it will likely stay in 3rd gear instead unless the hill is really steep.

Hope the new thermostat solves it! If not, one other thing you could do is add an HD cooling fan if you don't already have one. Here's a link for you.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=104&t=76451

Ted15 · **Posted:** Mon Apr 24, 2017 5:02 pm

lfhoward wrote:

Interesting. Maybe if they flushed every last trace of the original HOAT out of your system you could be ok. I know that HOAT and Dexcool do not mix together with good results.

In terms of the Tow/Haul button, when depressed it changes the shift points slightly (delaying upshift) and prevents the transmission from going into overdrive (4th gear). This will keep the transmission cooler and happier in situations where you are carrying heavy loads or going up steep hills where it would otherwise shift back and forth a lot between 4-2-3-4 etc. When Tow/Haul is engaged, it will likely stay in 3rd gear instead unless the hill is really steep.

Hope the new thermostat solves it! If not, one other thing you could do is add an HD cooling fan if you don't already have one. Here's a link for you.
http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=104&t=76451

I HIGHLY recommend the mechanical fan. I don't yet have one but after seeing the condition of the transmission fluid, I will. It was very burnt and black in color. I replaced my filter and changed out the fluid. I'll do it again after I put some miles on it.

lfhoward · **Posted:** Mon Apr 24, 2017 6:05 pm

My trans temp is super low now with the mechanical fan. Like 120°F or less most of the time! Coolant temp hardly ever gets above 215 either, even when towing.

Scar0 · **Posted:** Tue Apr 25, 2017 1:26 am

I run Zerex G05 antifreeze in my rig.
It is HOAT antifreeze and a lot cheaper then buying from a dealer.

Here is link to a thread/post for flushing the cooling system. See my first post there.
viewtopic.php?f=88&t=83260

chereveco · **Posted:** Tue Apr 25, 2017 5:12 pm

Read the recommended tread about the mechanical fan, I'll give a couple of weeks after the thermostat replacement, then do purchase....

Thanks

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chereveco · **Posted:** Wed Apr 26, 2017 4:07 pm

Update:

Got the thermostat, coolant.

I'll soil my hands this Friday.

Fan and clutch in shopping cart; waiting. ( Down here 90% of the roads are narrow and windy, lots of uphill driving, so the mechanic fan is a good investment. It will run like the old XJ, both mechanic and OEM electric ).

Also I have to adjust that darn useless parking brake. This Saturday I have technical inspection.

Let's see what is what....

Regards lost Jeepers.

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chereveco · **Posted:** Fri Apr 28, 2017 5:07 pm

Thermostat, replaced, parking brake adjustment done to the best that is possible...

Got to go to uphill and check if there's any difference with the new t-stat....

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3/4 overheat

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