Tempurature, thermostat and cooling discussion

Alak · **Posted:** Mon Jul 23, 2007 7:32 am

Some early morning musings.

Okay, so Im not the only one thats noticed KJ's (at least around here) run really hot. Like the heat is quite noticable from a few feet away when the fan kicks on. I've relayed this discussion with another liberty locally that, also, has an electric fan. The conversation basically started with, 'it runs pretty hot eh.' "Yeah it does."

I did some looking into the cooling fan, to see what I can do to get it to run on a more regular basis. It seems its run by a relay system. I dont have wiring schematics, or any repair manuals yet so Im not too certain on how exactly it works.

From what I gather its a 2-Speed system. I've only ever seen it work on 1 speed, which, considering the tempurature of the air coming off of it, is craptacular. Nothing is wrong with the fan or system, because everything is brand new, and never off-roaded. Tempurature guage reads correctly.

What Im getting at here is a way to get it cooler.

The Fan will only kick on at a certain tempurature. I wonder if theres a way to control this tempurature level. So the fan will kick on to a more sane level.

Thermostat. Are there other temperature thermostats availiable? I investigated locally in my limited selection and found nothing short of stock.

If the rad fan seems random on when it engages and dis-engages, I wonder just how hot the engine is accually running. AND how hot the transmission gets in stop and go.

I was thinking of installing my own electric fan relay, with automated tempurature setting. Im not so sure how this will the factory computer, settings or electric fan system and set off an engine check light.

Im also going to look into installing some Autometer guages, like Transmission Tempurature, Engine Tempurature, Engine Oil Pressure and Tempurature guages. Hopefully I can avoid clutter.

WoodysKJ · **Posted:** Mon Jul 23, 2007 7:53 am

I am not sure this question belongs in the off road section. I would post it in the General Disscussion area.

Alak · **Posted:** Mon Jul 23, 2007 8:04 am

Opps. I did it again. Mods, please move me.

Didnt realize it was in the wrong section.

tjkj2002 · **Posted:** Mon Jul 23, 2007 9:40 am

The KJ runs at 210-212 degrees at operating temp.There is so far no known lower temp T-stat,just the 195 degree stock one.Just remember you would need to reprogram the PCM to have the KJ run right with a lower T-stat or running at lower than the normal operating temp.As far as feeling the heat off the KJ,that's normal,when the fan kicks on the hot air got's to go somewhere.

I can't say for the newer KJ's with the 42RLE tranny but when I pulled a 5000lbs trailer 1500 miles through the mountains I used a laser temp gun to keep track of the tranny pan temp.Before the trip I checked the pan temp and it averaged about 130 degrees,when towing it was between 135-155 degrees.Though I have a massive Aux tranny cooler in tandom with the in-raditor cooler.Though just taking the pan temp is not correct it gave me a good idea on where the tranny temps where.I was always taught to keep a auto tranny fluid temps between 130-180 degrees,any colder and the tranny is sluggish,any hotter you burn the fluid and cook the tranny.

sleeve84028 · **Posted:** Mon Jul 23, 2007 10:45 am

With the small engine compartment and the super heating abaility of the 3.7L the underhood temps do become "noticable" when you are doing a walk around or standing at the gas station. However, I have never once notice a problem with overheating in my KJ.

I'd just leave well enough alone with the fan.. It works great at keeping the needle in the middle of the gage so what is there to fix? You could possibly buy an additional fan and front mount it to the A/C condensor and then hard wire it with a DC Controller (like this one) to get some added cooling of the system but I don't know what kind of $$/benefit you would realize by doing so.

WoodysKJ · **Posted:** Mon Jul 23, 2007 11:05 am

On a little bit of a topic Hi-Jack...

Where do you check the temp on the tranny's with the laser temp? I had a disscussion with my stealer about the lack of a tranny dip stick and he said that Miller tools makes a special tool for checking the tranny fluid in conjunction with a laser temp guage. what ever the temp guage says there are fluid levels on the dip stick for the proper fluid at that temp. Ideally he said it should be check around 110 degrees F.

whats up woth all that?

Jeepjeepster · **Posted:** Mon Jul 23, 2007 1:11 pm

Ive towed in mountains, offroaded in 100F heat, and sat in the heat of bumper to bumper traffic and Ive never had a problem with over heating.

If you want more cooling, look into getting the engine driven fan that comes with the towing pack.

Alak · **Posted:** Mon Jul 23, 2007 1:40 pm

I was talking to an SRT enthusiast earlier today and he said lowering the T-stat temp would improve engine efficency and overall performance. He gained .1 second on the 1/4 mile with his Cherokee SRT-8. A reprogram of the PCM would not be required. However, he said, the fan would kick on at the set tempurature, therefore partially voiding the change in T-stat.

I guess Im a little paranoid because of my trail accident a couple months ago (when the rad fan failed). My uncle said also to consider oil tempuratures, since the oil does cool most of the moving components.

There must be a way to improve under-hood temps.

--------------------

On a side note;

Im considering the switch to a stand-alone engine management system. I know it seems like a little much, but I have an old Haltech E6X sitting here that would work very well with the Powertech I think. I could install some headers, remove the cats (no emmissions here) and beef up the exhaust. I could also tune much better for fuel economy and/or performance.

Reason I havent done so already is Im waiting for the warrenty to run out so I can slip a 4.7L or Hemi under the bonnet.

Jeepjeepster · **Posted:** Mon Jul 23, 2007 4:28 pm

The engine is tuned to run at a certain temp. Are you sure that guy knew what he was talking about?

tommudd · **Posted:** Mon Jul 23, 2007 4:55 pm

A few years ago some vehicles would allow you to put in a lower thermostat and it would help HP and mileage anymore dont think so. Everyone talks about the Lib running hot but have you ever walked in front of a 4.0 Cherokee after a good run? I think they ran as hot ot hotter than the Liberty and all of mine well 3 Cherokees all ran up into the 245/265000 mile range with no problems. I think I will let mine the way it is! :wink:

tom

Alak · **Posted:** Mon Jul 23, 2007 11:10 pm

Jeepjeepster wrote:

The engine is tuned to run at a certain temp. Are you sure that guy knew what he was talking about?

Mopar offers 3 different Thermostat ranges for the SRT8 Cherokee. He said the stock is the highest, for all around climate. Since the weather in so unpredictable here is brutal here, he ran the middle thermostat. Never know here, it can snow in 100F day in July. I've seen it happen, only once.

My concern about the heat, is the plastic intake manifold and aluminum heads. I've seen KJ's around here with darn near 200,000 Miles, but they all either burn coolant or oil, or both. Not in large quantities, but its apparent.

Pablo · **Joined:** Thu Feb 02, 2006 10:06 pm **Posts:** 1201

I am not worried about the engine as much as the whole compartment. I think getting it a bit cooler under there would help the longevity of rubber and electrical and you might pick up some power too.

You may want to look at these threads, about hood louvers:

http://www.lostjeeps.com/forum/phpBB3/vie ... hp?t=20343
http://www.lostjeeps.com/forum/phpBB3/vie ... e03332464e

http://www.raceace.com/

GPR65 · **Posted:** Tue Jul 24, 2007 6:29 am

you can use a 180 or 185 thermostat from jet chip and use the one for the cherokee. on a hot day with air (air on means it runs the fan constantly) i never see above 195 with my scanguage and thats idling. going down the road its more like 191- 193. my dads 02 chrysler minivan idles around 209 and drives at like 206.

Chris

Tempurature, thermostat and cooling discussion

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