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4.0 operating temp #1651782
07/27/14 09:12 PM
07/27/14 09:12 PM
Joined: Mar 2005
Posts: 3,053
Central NC
gch Offline OP
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gch  Offline OP
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Central NC
My 4.0(1998) seems to run at 210* and I from what I gather most others do as well.With a 195 T-stat and running at 210 I would say that is a weak/underperforming cooling system.Have any of you guys run a 180 t-stat to bring the operating temp down w/o having adverse effects(mileage,etc.)?

Re: 4.0 operating temp [Re: gch] #1651783
07/27/14 09:26 PM
07/27/14 09:26 PM
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J_BODY Offline
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Need more capacity in the cooling system for the 180 to work. Out here in the desert I've seen water resivoirs attached to front aftermarket bumpers and many run the larger aluminum radiator. Just some things I've noted with the Cherokee crowd.

Re: 4.0 operating temp [Re: J_BODY] #1651784
07/27/14 10:36 PM
07/27/14 10:36 PM
Joined: Jan 2007
Posts: 7,664
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ahy Offline
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My daughter's 4.0 always seem to run at 205 also with both "old" and "new" stat. A couple of years ago we ran it from IL to CA through Phoenix in the summer. It was a pretty much steady 205 all the way... maybe a few degrees warmer pulling a hill at 100+F and a few degrees cooler descending a hill in cool weather.

I just think that's how they run. Perhaps it has something to do with the stock gauge or placement of the sensor. As long as it seems to regulate around 205 I wouldn't worry or change anything.

Her Jeep had 100k when we made the long run with the trailer and now has 135k.

Re: 4.0 operating temp [Re: ahy] #1651785
07/28/14 03:39 AM
07/28/14 03:39 AM
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Elk Grove, Calif.
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bigblock340power Offline
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I have a 1998 Jeep GC with a 4.0 six. 195 thermostat, runs all day between 200/205 in 100+ heat. Even in the winter it runs the same temp. A few years back it wouldn't heat up. Pulled the stat and found that the stat had stuck open. Only issue I've ever had with the cooling system.

Re: 4.0 operating temp [Re: bigblock340power] #1651786
07/28/14 04:14 AM
07/28/14 04:14 AM
Joined: Jan 2011
Posts: 4,785
Utah and Alaska
astjp2 Offline
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200-210* is normal, ping doesn't happen until 220*...I have a stroker and its compression was running about 215 psi, I started to have overheating problems with my warn winch. Aluminum radiator helped but it was not enough...I had to drop the compression and put in a 180 stat to get it under control. My wifes 4.0 never has a problem, even with the AC on and 100* temps, only gets to 215*. Tim


1941 Taylorcraft
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1994 Wrangler
1998 Wrangler
2008 Kia Rio
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I didn't do 4 years and 9 months of Graduate School to be called Mister!
Re: 4.0 operating temp [Re: gch] #1651787
07/28/14 03:59 PM
07/28/14 03:59 PM
Joined: Apr 2010
Posts: 10,545
Sunny South Florida
Golden-Arm Offline
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Sunny South Florida
that's not really hot. the 195 number is where it opens, not what temp you'll run at. 10 degrees hotter than the stat, isn't anything to sweat.

running a cooler stat won't necessarily make you run cooler. it will just open sooner. it regulates temp to a point, but the engine is going to run at a temp, it's going to run. use a high flow stat, if you want. remember to put a "burp" hole in the disc, if it doesn't have one already to prevent air pocket.


"When Tyranny Becomes Law, Rebellion Becomes Duty"

Re: 4.0 operating temp [Re: Golden-Arm] #1651788
07/28/14 06:21 PM
07/28/14 06:21 PM
Joined: Dec 2005
Posts: 1,115
Cruising!
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QuickDodge Offline
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My 4.0 Cherokee used to run at an indicated 210 degrees. I was never concerned about it. Back in the days when 160 and 180 degree thermostats were common, 210 degrees would have been considered hot. Since the car manufacturers switched to 195 degree thermostats, most vehicles run at temperatures over 200 degrees. A hotter engine means better gas mileage and lower exhaust emissions.

Some folks say the cooling system on the Cherokees is marginal. I never had any trouble out of mine, but my Cherokee had an easy life.

Last edited by QuickDodge; 07/28/14 06:28 PM.
Re: 4.0 operating temp [Re: gch] #1651789
07/28/14 10:14 PM
07/28/14 10:14 PM
Joined: Mar 2005
Posts: 3,053
Central NC
gch Offline OP
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Central NC
I just recently got mine on the road.The gear head in my thinks cooler temp more power but that isn't what this was designed to do.It surely doesn't need to get worse gas mileage lol so I will leave it and concentrate on other areas.I did a coolant flush saturday as it has been sitting for 2 years prior to me getting it 5 months ago.
As long as it doesn't cost me anymore money that it has to get safely running and stopping I will be ok.I am driving it everyday for a bit to make sure all the bugs are worked out then it will be a third car/inclement weather vehicle.







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