JK 3.6 Thermostat

I have a 2015 JKUR and am fighting an overheating issue since November. We’re full time RV travelers, so it’s hard to have the same shop do repairs with follow-ups.
We started with getting warm climbing a hill outside of Las Vegas in October, outside air temp 70- 80, vehicle speed 60 (wife driving behind me towing our fifth wheel), engine temp rose to 240 (fans on). Had coolant replaced in Pahrump when oil changed. Shop used Chrysler purple.
After coolant replaced, had cel for thermostat not allowing temp come up fast enough (outside temp in the 40’s, engine coolant temp after driving 7 miles at 55 mph 184). Had thermostat replaced in Bullhead City, Az with CarQuest part, and was told it’s a high failure item. Shop used Zerex G05 to top off. Temps ran normal after that.
Approx 500 miles later, and in Salt Lake City, had engine temp climb to 250 at vehicle speed 70 with 30+ headwind, outside temp in the 40’s. Had thermostat replaced with MotorRad as MOPAR was back ordered. Zerex G-05 used to top off again.
Approx 1000 miles later, driving at 65 mph with a 30+ headwind, and a slight (maybe 2% climb), outside temp 40, engine temp climbed to 240, slowed to 62, temp stayed steady at 231. Turned around, ran at 62, temp stayed at 228.
Stoped at Chrysler dealer, told thermostats are National bad order of over 55,000(!). Ordered one, get well of 45 days (we’ll see). Went to Napa and bought new stat there, plus water pump (I think a slight chirping from it when cold, replaced idlers and tensioner, no fix), got 2 gallons of Zerex G-05 full strength (will mix with distilled water), and BG coolant helper, plus new serpentine belt.
My plan is to drain as much coolant as possible, use air to blow out block, pour distilled water thru rad, run distilled water thru block, replace pump and stat, new belt, 50/ 50 coolant and distilled water.
Is the stat a common failure item? The Jeep has 62,000 miles, and thermostats don’t (in the past fail very often). The rad seems clean inside, and the heater will cook you out. Any other ideas?

 

Just a few thoughts since multiple parts have been changed and some more than once: 1) radiator may be restrictive reducing efficiency, 2) certain types of coolants should not be mixed 3) OEM thermostat, 4) thermostat installed correctly, 5) fan(s) defective, 6) obstructions to air flow from winch , lights etc

 

I agree with @aggrex . Numerous parts swapped and still an issue. The main issue I see reading your post.
You should NEVER mix coolants. Use only what is recommended for your model Jeep. My Owners Manual states to use only OAT (Organic Additive Technology)coolant. I have a 2016 JK. Problem with mixing coolants is it turns to sludge and could possibly clog the small cooling channels in the radiator and motor. And its are good for 10 years /100k. Also, it's been my experience that thermostat are NOT a high failure part. But it's entirely possible there is a manufacturering defect with a certain manufacturer. And I would think that retailers would pull them off the shelf.

So since your so deep into this. I would definitely swap coolant and Stat. How did you determine the water pump was bad?

 

Thanks for the ideas. Since I’m a full time Traveller and don’t have a shop, I have to take certain short cuts I don’t like, like using outside shops for repairs. I’m currently near a military base and have access to the base hobby shop, and am only doing this once, hence the reason for shotgun gear the parts. the water pump is chirping when cold, but stops after warming up, and again, since I have access to a shop right now, it’s going away. So is the belt, thermostat, and radiator.
Again thanks for the ideas.

 

Good luck @tim2015jkur . Post up your results.

 

The thermostat housing on a JK 3.6 (and other applications of the 3.6) is a pretty micky mouse affair and they do fail. Mine also threw the code for excessive warm up time. I just deleted it----- It only occurs when the ambient temperature is cold and still runs normal temp when warmed up. Someplace I recall Dorman was making aluminum replacements for those which would be a good upgrade. At least they are easy to change out. Sort of akin to that also micky mouse plastic oil filter housing.

JK fun. It would take a whole page of 8 font to describe all the stuff that has gone to crap on mine and it still only has 64k on the odometer. Out of the approximately 40 vehicles I've owned over the years, it is the only one I've tagged with a moniker: POS. With soooooo little additional effort it could have been sooooooo much better. In my case, it is very likely going to get sold when I get the Willys CJ3B back together which should be soon. The ONLY thing I'll probably miss is the AC on the way to the trailhead. And there will be a much broader grin on my face again. From 3.5 decades back:

 

agree with the others, don't mix coolant. Also make sure you use the correct color for your jeep. I have a 2012 JKU and mine is green color coolant and 2013 JKU is red color coolant. So look up in your manual or google to see what color coolant you should use because if you use the wrong one it will create sludge and lead to many other issues.

In regards to the thermostat it is a very easy fix, and you could probably do it yourself, I've done mine. it's literally 4 screws total to get it swapped out. $15 part. That should at least save you some money if you still need to keep doing it til you find the issue.

 

Here’s an update:
Replaced radiator with O’Reily’s replacement, only thing available immediately. Will watch for an all aluminum eventually.
Replaced thermostat with Napa lifetime. No MOPAR thermostat available for “maybe 45 days”.
Replaced water pump with Napa/ Gates.
Replaced serpentine belt with Gates.
Flushed with 4 gallons of distilled water.
Reserviced with 1 1/2 gallons of Zerex G-05 coolant.
Drove at 75- 80 mph for 30 miles, had slight climbs, some headwind, and altitude of 4500+/- feet.
Coolant temp would rise to 221 when at full throttle, but not get higher. As soon as throttle set to maintain speed, temp dropped to 215-217.
Drove about 200 miles since in varying traffic and speeds, temp stays at 215-217.
I’m calling this fixed.