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Now I need a thermostat ! GRRRRRRR

6K views 19 replies 11 participants last post by  simioh 
#1 · (Edited)
32k miles on a 2012 JGC, leaking power steering fluid and now I get a check engine light. PO128, coolant. Now I have to change the thermostat. Really? Who would want to buy these pieces of crap? PS, I have two Ford products also, 128kmiles and 90k miles. Nothing but oil and filters.......................... This seems to be a common problem with JGC of that age.
 
#3 ·
I have a 2012 with 80k on it and no problems. Also I had two Fords before this, both 2013's, and they had GARBAGE transmissions. One would slip constantly, the other would shift so hard from 1-2 that it would snap your neck. Neither had more than 30k on the odometer. So not sure who would actually want to buy those pieces of crap. Everybody has their own opinion I guess.
 
#6 ·
Took me 30 min and $10 to swap my thermostat. Not super difficult. I got the same code after it was pretty cold one night then the next morning I ran it up to 5,800rpm without thinking about it not being warmed up yet. Got the code, swapped it out, easy cheesy lemon peasy.


Sent from my iPhone using JeepGarage
 
#10 ·
Yes, and I have used that exact one.

Depending on outside temperature and driving habits, you will throw a low temp code...

The code is set if you do not hit 186 degrees within a certain time frame ( approximately 16 minutes I think).

In my situation, I am less than 1 mile from a highway with a 65MPH speed limit. So we typically leave home and set the cruise almost immediately. With the thermostat opening at 180, and the high amount of air flow for the first 20 minutes, we would get the code almost every morning.

Remember if you don't also re-program the fan on temp, then the low temp thermostat only helps while moving. So some can get away with it because they are in stop / go traffic where it has time to creep up closer to 190 within the allotted time frame.

So when going with a lower temp thermostat I either recommend no less than 190 (and not a lot of options at that temp) or preferably, go ahead and get a custom tune on the vehicle. Not only does that allow you to set the fan on temp lower so you take advantage of the lower temps even when sitting still but it also can be custom tuned to eliminate that code all together.
 
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#13 ·
Helps retain some HP that would be lost due to engine heat soak.

Especially noticeable in city driving. (Stuck in slow bumper to bumper traffic, finally get an opening or your freeway entrance comes up.)

For those really pushing things, it allows you to increase the engine timing without detonation.

And they are cheap! IMO it's really one of the best bang for your buck performance mods.
 
#15 · (Edited)
So I should clarify, I am not sure how it compares or how much it benefits the smaller engines. My personal experience and research is primarily for performance vehicles and even more specifically the 5.7 and 6.1/6.4.

The best data I know of, or at least the data that most closely ties to the 5.7/6.4 Jeep, was completed a long time ago over on LXForums.

If you look at the last set of data in the first table you will see a 170 degree thermostat consistently dynoed ~10HP higher than the same setup with a 203 degree.

GIFO3 - Headers, 18" vs 20" & GSM Mod RESULTS

Now this test was not originally intended to be just for the Tstat so you will see a lot of other info there unrelated to this discussion. This is just the best, back to back, direct comparison for these engines.

A quick google search will yield hundreds of articles about the idea in general. Either search for Low Temp Thermostat advantages or for a more technical take, search for engine temperature effects on detonation.

Finally, I think most with an SRT or 5.7L will agree that these machines put out a LOT more in the cooler months. Sure, this is related to intake temps and lower temp coolant doesn't directly affect them, but keeping everything in the engine bay running 20 - 25 degrees cooler, I would think, would help lower all of the ambient air available. Even if running stock air boxes, the air still has to pass through the Throttle body and intake.. Couldn't hurt if those were all a few degrees cooler.

Additionally, having ran low temp Tstats in all my cars since 2005, and being VERY happy with the end Dyno numbers of each, many of them running 10 - 20 HP higher than the same mods (minus Tstat) for others, I came to the conclusion that at the very least, it wasnt hurting anything, and possible, it is helping. (And being a realist, its possible that the barometric pressure or dyno settings were different or I was running better gas or any combination of hundreds of variables.... My own experience isn't scientific by any means)

I admit, it's difficult to determine fact from opinion, and I too may not be correct on my final determination... A lot of my own is circumstantial evidence but between that, the test above and the fact I can find a lot more articles on the pros over the cons, and again, the cheap cost, Its always been one of my first mods.
 
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#16 ·
The biggest misunderstanding about thermostats is that people believe they make the engine run cooler. The thermostat can only determine when the cooling system is allowed to start cooling the engine, it basically sets the floor and not the ceiling on engine temps.

The most important fact to remember is the cooling system and load on the engine determines how hot the engine gets, a thermostat fully open will still be the mercy of the coolant system's ability to remove heat. But lets say that you can and we installed a 180 degree thermostat. Keeping in mind, your cooling fans are designed to cycle ON & OFF and are NOT designed to run continuously.

First you have to maintain that 180 degrees constantly that could possibly drop you air intake temperatures a few degrees. But in order to take advantage of this, your engine must be capable of maintaining this 180 degree, this is normally accomplished through high flow thermostats, auxiliary electric fans, lower cooling fan settings, cooling fans staying on longer, running a high water content in the coolant, etc. But this isn't without its drawbacks. the major drawback is a loss in gas mileage due to the internal combustion engine losing efficiency at lower temperatures and that denser air charges also require more fuel to maintain the proper air fuel ratio.

In the end, we have the potential for the following, terrible gas mileage, increased engine wear due to the lack of part expansion which is calculated in to the engine design to take up certain clearances, increased particulate matter in the oil due to less efficient combustion and much richer mixtures.

Always remember, you need four things to make an engine run, Air, Fuel, Spark and Compression. Increasing these parameters in the right ratio and you'll make more HP.

I hope this helps
Michael Plummer
 
#17 ·
All very true and appreciate the info. Especially for those who may come across this thread in the future.

I do run my fans at a lower temperature and have never seen a decrease in mpg. If anything, it has increased but the custom tune includes other timing adjustments that could be making that change.

In my use and area (climate and driving characteristics), the stock system is very capable of maintaining 184 degrees.

Additionally, I used to send my oil off for analysis fairly regular and even after use of a 180 for 8 years and 160,000 miles, never saw any abnormal wear.

That is why I stopped at 180 though, even though the dyno showing the gain, was at 170. Seemed to be pushing it just a bit far for me.

Your information is exactly what I meant when I said many cons can be found when searching the Internet. Great to have it here to compare to the potential pros for others to help make up their own decision.

I am just one persons use case, in my own research I found more with positive things to say than potential negatives and my own use has been positive.

But to each their own.
 
#18 ·
The test with the 170 degree thermostat in my opinion isn't a valid test. First off, they disconnected the battery between the two thermostats. And they also started the test at different ECTs. They could of started the other test (higher thermostat) at the same cooler ECTs as the 170 degree thermostat but they didn't. In order to do a better comparison, they need to limit the differences.

If what you're saying is accurate, that your gas mileage increased and the lower ECTs has an effect on IATs. How is it possible that a more dense air charge doesn't need more fuel. Remember, Air, Fuel, Spark and Compression. If you increase your air flow, you will need to increase fuel or you'll be leaner. You stated you have a custom tune, are you running leaner? If you're running leaner than your increase in gas mileage is due to you runner leaner and not a cooler thermostat.

OEM Engineers especially JEEP Engineers would love to have the luxury of better MPG with the Hemi engines but it's not as simple as running it leaner or using a lower thermostat without a trade off.

Bottom line, your truck (BTW, nice one) and your money and you can do whatever you like. And I agree, nothing wrong with a discussion about your experiences and Pros and Cons.

Thanks
Michael Plummer
 
#19 ·
Apologies, did not mean to imply the thermostat alone helped mpg. Only meant to indicate I have not seen a mpg decrease.

I just re-read previous statement and did not word it well.

I did the tstat at the same time as I did the tune. (Insured I did not set the code mentioned above, lowered the fan on temp / target temp and yes it adjusts timing).

The tune is likely what helped mpg but was trying to show that IF the tstat hurts mpg, it is minimal as my net result of tstat and tune was mpg increase.

As far as the test goes, the battery pull was to try to ensure a fresh start, no set adaptives that might mess with the results. But as said in the notes, the low temp thermostats part of that test was a last minute add.

I thought somewhere on that forum someone actually listed the amount of timing that was pulled at the higher temps (based on fuel and spark tables originally stored). I couldn't find it though so maybe I dreamed it or maybe it was just part of the discussion when I originally had the Magnum done...

Definitely makes me want to test it now, but I doubt I'll find the time. I haven't sent the Jeeps oil off for analysis yet, will do that next oil change, just to be sure. I really expect I'll still be an advocate but hey, never know.
 
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