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Old 05-15-2012, 10:05 PM   #1
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Question 2012 Pentastar engine heat issues

Purchased a 2012 Unlimited Rubicon (3.6L Pentastar V6) last winter. Now that the weather is warm, when wheeling or towing small camp trailer, the engine can run up to 5/8 to 3/4 on the temp guage. Is this normal?

Had a 2007 Sahara with the 3.8L V6, and never saw temp guage go above normal even in summer wheeling in Utah deserts.

Any ideas?

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Old 05-15-2012, 10:18 PM   #2
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haven't towed with mine, but the temp gauge has never gone over the 1/2 mark. have you cleaned your rad after wheeling?

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Old 05-15-2012, 10:52 PM   #3
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mine goes straight to half and hangs out there. even in traffic in 90 degree heat it was at half. even after sitting for 2 hours and starting it up it was at half.

and i believe it, this engine is seriously hot. i could barely open the hood and put the prop in. it was like eating a hot pocket right out of the microwave.
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Old 05-15-2012, 11:07 PM   #4
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Yep, did a thread on this a while back. It stays hot for a while too after being off.
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Old 05-15-2012, 11:16 PM   #5
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Actually this past weekend i was driving back from camping in my 2012 rubi 6-speed fully loaded with camping stuff all the way to the top and 4 people inside. Going up a high hill on highway in 5 or 6th the temp gauge did go up a bit. But I also have a winch sitting on my stock bumper covering half of radiator. Temp came back as soon as road leveled out, so I guess its ok. Should i be concerned?
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Old 05-15-2012, 11:18 PM   #6
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Add some Water Wetter to the radiator. It helps the engine transfer heat to the coolant more quickly.
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Old 05-15-2012, 11:23 PM   #7
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wonder how this will affect longevity of the new pentastar.
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Old 05-15-2012, 11:32 PM   #8
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If your between hash marks your fine. If you really want to know coolant temp, buy a blue tooth obd2 devise and use the application Torque on your smart phone.There are also many low priced hand held devices that will do the same. Dont depend on the analog gauge as a accurate measure of coolant temp.
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Old 05-16-2012, 09:03 AM   #9
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And wear thick socks....Mine seems to bake the drivers side.
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Old 05-16-2012, 10:52 AM   #10
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Originally Posted by BlueRubi12 View Post
Purchased a 2012 Unlimited Rubicon (3.6L Pentastar V6) last winter. Now that the weather is warm, when wheeling or towing small camp trailer, the engine can run up to 5/8 to 3/4 on the temp guage. Is this normal?

Had a 2007 Sahara with the 3.8L V6, and never saw temp guage go above normal even in summer wheeling in Utah deserts.

Any ideas?
I think this is something you want to look into. Schedule a service appointment and see what they say, at the very least you'll have it documented in case it does overheat down the road.

I would also look into a OBD-II device so you can monitor the actual temps...
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Old 05-16-2012, 02:18 PM   #11
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Wink Pentastar Heat Issues

Thanks for the help. Could someone please clue me in a little more on the OBD II device, and is there an Adroid ap for it?
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Old 05-16-2012, 02:20 PM   #12
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Thanks for the tip. I'll try to find some Water Wetter. Assume it's at most auto-part stores?
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Old 05-16-2012, 03:03 PM   #13
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Thanks for the tip. I'll try to find some Water Wetter. Assume it's at most auto-part stores?
Water wetter is commonly used in racing motorcycles. You should beable to find it at bike shops or fine automotive shops, unlikely at walmart, pepboys etc...
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Old 05-16-2012, 03:09 PM   #14
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Water wetter is commonly used in racing motorcycles. You should beable to find it at bike shops or fine automotive shops, unlikely at walmart, pepboys etc...
My local autozone carries it and i believe advanced auto it has become pretty common in street modified cars/trucks past few years alot of guys near me swear by out ive used it on a few cars ive owned with good results
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Old 05-16-2012, 06:22 PM   #15
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Interesting. When the "heat problem" first appeared I was towing a small camp trailer and had my Ramsey Patriot 9500 winch mounted on a Ramsey mount over the stock bumper. Was trying to avoid the rust problems from all of the winter salt out here that I had on my 2007 Sahara - Best Top bumper. Anyway, my mechanic at the local Jeep Dealer, Doug Smith Jeep, told me he would bet me money the wich was blocking too much of the airflow. So, last Sunday, I pulled off the wich and have been driving around without it to see if the problem is gone.

Mostly, but Monday I did a short trail near home in 4 low up a very steep grade, crawling around 4 to 5 mph -- with the air conditoning on -- trying to purposely stress the vehicle. The temp did climb to 5/8 on the guage. Went immediately to the shop and asked the man. He said under those conditions that would be about normal for the Pentastar. ??? My old 2007 3.8L never, ever went above center on the guage.
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Old 05-16-2012, 08:05 PM   #16
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Never towed, but the gauge has never been above half. It warms up super quick and stays there.
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Old 05-16-2012, 08:09 PM   #17
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Dont forget that gauges are just approximate and not nearly as accurate as a dedicated direct connect aftermarket option. I refer to the factory gauges as dummy gauges, they give you an idea, but dont bet the bank on em.
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Old 05-16-2012, 08:17 PM   #18
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Take it into the dealership to have them do a once over.

Make sure the dealership tests it under similar conditions.
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Old 05-16-2012, 08:40 PM   #19
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FYI, the factory temperature gauge isn't really a gauge at all. It's more like a 4 position indicator.

I don't know the exact numbers for the Pentastar, but the method of operation is the same. Here's the info from the old 3.7L:

The gauge slowly climbs towards the middle as the engine warms up, then stays locked dead center as long as engine temp is less than 255*F.

If the engine goes over 255*F the gauge is moved to the 3/4 position to indicate "high" temperature.

If the temp reaches 269*F the gauge is moved all the way to the right to indicate a "critical" temperature.

It gives you a rough idea of whether or not your engine is at an appropriate temperature, but don't expect it to tell you anything meaningful.

The best way to look at it is "cold, warm, hot, danger"
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Old 05-18-2012, 02:59 PM   #20
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But is it normal for it to go to hot state under certain conditions or it should be dead center anytime if it operating normally?
Thanks
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Old 05-18-2012, 04:02 PM   #21
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and i believe it, this engine is seriously hot. i could barely open the hood and put the prop in. it was like eating a hot pocket right out of the microwave.
No one, with the exception of Chuck Norris, can eat a hot pocket right out of the microwave.
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Old 05-18-2012, 04:58 PM   #22
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3/4 on the temp gauge is still "Normal." My s2000 does this as well under stress. An engine has a operating temp RANGE, and on the dash, it is from 1/2-3/4. You should not see anything above 1/2 on the gauge during normal highway driving, but if your rig is loaded/towing, sitting in bumper to bumper traffic/climbing, has the AC on, it is NOT uncommon for the temp gauge to rise to the level you are describing. You are all good.
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Old 05-18-2012, 09:22 PM   #23
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I don't think it is normal, the temp is controlled by the thermostat, which restricts or opens to get to and stay on normal temp, above half and I would get anxious, I would say it is not normal, meaning the cooling system is not coping, something is restricting water or air flow.
I have done lots of towing in very hot weather, and always expect the gauge to stay in the middle.
My 5 cents worth is to have it checked out, the dealer will tell you that is okay, but don't accept that, make sure it runs normal.
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Old 05-18-2012, 10:38 PM   #24
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I don't think it is normal, the temp is controlled by the thermostat, which restricts or opens to get to and stay on normal temp, above half and I would get anxious, I would say it is not normal, meaning the cooling system is not coping, something is restricting water or air flow.
I have done lots of towing in very hot weather, and always expect the gauge to stay in the middle.
My 5 cents worth is to have it checked out, the dealer will tell you that is okay, but don't accept that, make sure it runs normal.
A thermostat does not "control" the temperature like it does in your house. A thermostat in a car tells other things what to do, like kick the fans on. It does not stop your rig from getting hot from heavy duty work. I can take any rig on this forum, and drive the temp to 3/4 on demand. I've done it in rental cars when I was driving in Utah, in the summer, climbing up a steep road.




Everything WITHOUT the red on your gauge is considered "normal." ONLY the red area is considered "overheating."

This is a photo from my 2012 manual.



Again, 3/4 is MORE than normal.
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Old 05-18-2012, 11:47 PM   #25
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I only have 2K miles on mine, but the hottest I've gotten it was about 5/8. I was on a 12% grade behind someone going slow when I realized I also had my A/C on. It still surprised me.
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Old 06-03-2012, 07:02 PM   #26
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Cool PentaStar Heat Issues -- Heads UP

Thanks for all the help and suggestions. The dealer finally found the pressure cap was defective and letting off pressure at 10 psi

Here's the reason I'm posting this again. When they put on a new cap, the MOPAR specs show a 17 lb cap. However, the old cap was 18 pounds. All the new Wranglers (2012) at the dealer have 18 pound caps. So, I drove around a couple of weeks with the "right cap" (the 17 lb'er), and when it was hot one day while going up a mountain road (paved highway), there goes the temp guage again up toward about 5/8 on the scale until the road leveled off. So I started a little detective work, and found that MOPAR says 17 lb cap, but factory installs 18 lb cap

I just bought a new 18 pounder from O'Reilly's (about $5) and put it on this morning. Took the same mountain road again today while even hotter than the other day. Tooled up the road with the AC on, and nothing. That guage stayed right in the middle

Still want to do more testing, like pulling the trailer, but I think the heat issue is mostly solved.

So, if you are having any heat problems with the new 2012 Pentastar engine make sure of two things. 1. Test everything -- thermostat opening temp, cooling fan start temp, and lastly radiator pressure. 2. Look at the cap on the Jeep BEFORE disposing of it, if it failed the pressure test. If it says "18lbs" on the cap, then put on a new 18 lb, not the factory "spec'd 17 lb".

Maybe Chrysler is in the process of tweaking the cooling system, but if that old cap was "18" then put on a new "18".
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Old 06-03-2012, 07:58 PM   #27
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No one, with the exception of Chuck Norris, can eat a hot pocket right out of the microwave.
The most interesting man in the world eats hot pockets while they are still in the microwave.

Stay thirsty my friend.............
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Old 06-22-2013, 02:42 PM   #28
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My 2012 Wrangler has been back to the dealer 3 times for a heat issue. Noticed uneven heat from the dash a few months ago. Drivers side cold, passenger hot. Long story short, the radiator, heater core, thermostat and cooling fan have been replaced. They installed a filter screen in the heater core hose which clogged up and was removed. The material in the screen was clay like, casting material I assume. The clogging caused an over pressure condition and coolant was blowing out of the cap. My cap is an 18lb. unit. Another obstruction was discovered in the heater core hose. System flushed twice, new coolant, three times. My coolant was cloudy/ milky. Still at the dealer hope to get it back Wednesday.
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Old 07-09-2014, 03:20 PM   #29
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I found this post with no follow up. Too bad. I would like to know if the cooling issues were solved.

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