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Old 03-23-2015, 09:05 PM
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Thermostat rationality

I recently got a code "P0128 thermostat rationality" on my 2015 Jeep SRT. I first had a Jet 180 thermo and recently switched to a Mishimoto 180. Anybody else ever get this code? Is there a way to clear and see if it comes back without going to dealer?

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Old 03-23-2015, 10:35 PM
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I installed a jet 180 from almost new on my.2014. Not a single problem. Why did u switch from jet to mishimoto?
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Old 03-23-2015, 11:13 PM
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Re: Thermostat rationality

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Originally Posted by Scottina06 View Post
I installed a jet 180 from almost new on my.2014. Not a single problem. Why did u switch from jet to mishimoto?
I felt like temps were getting to high with the Jet and I was going to just buy another Jet in case mine was faulty but decided to try a different brand 180. Temps were all over the place with the jet and would climb as high as 221* at times when sitting in traffic. The Mishimoto has never gone above 212* so far but seems to hold at 185* most of the time.
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Old 03-24-2015, 02:31 AM
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Thermostat rationality

We have that code with a Jet as well as many other 180s....

Happens on our 2015, happened on our 2012, our 2006 300 and 2005 Magnum.....

The system must see 181 degrees within a certain time frame from initial crank.... I believe it's about 10-12 mins....

The thermostats open between 178 -180 degrees... We have the killer glass radiator tubes on the 300 & Magnum and would start to see a trickle flow as low as 176 but always substantial movement by 178....

For us, we have less than a quarter of a mile before getting onto a 65MPH highway. So the engine is still relatively cool when we set the cruise around 68MPH....

With all that airflow through the radiator we see it hit 179 degrees and sit there.... So as a result, we set that code 2-3 times a week!!!!

If we let it warm up for the full 10 minutes at idle, no problem, and when leaving work (stop and go traffic) no problem....

A custom tuner can stop the code with a custom Diablo tune...
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Old 03-24-2015, 05:47 AM
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Re: Thermostat rationality

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Originally Posted by Daniel454 View Post
We have the killer glass radiator tubes

...
Say what???? Any chance you have pics and a link of where to buy. I've never heard of glass tubes.
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Old 03-24-2015, 10:38 AM
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Re: Thermostat rationality

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Originally Posted by DCRSRT View Post
Say what???? Any chance you have pics and a link of where to buy. I've never heard of glass tubes.

They don't make one for the Jeep directly. The ones I have are on my Mag and previous 300....

(No pics in my phone but can post some later)

BUT the Jeep has a long straight hose up front so I am sure just replacing the straight section would still look "Killer"... :-)

(And a lot more glass than I was able to showcase in the 300/Mag.)

Or they can do custom ones, for a price of course...

Here is the website, many over on the LX forums have been running them for years. I myself have had no problem in 8+ years and over 100k miles..

http://www.killerglass.com/
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Old 03-24-2015, 11:28 AM
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Re: Thermostat rationality

Anybody know of a way to clear code without going to dealer? Is there a fuse I can pull and disconnect battery?
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Old 03-24-2015, 11:58 AM
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Re: Thermostat rationality

4 good cycles will clear it. Meaning, start the car and let it get to 181 or greater 4 times in a row. It'll go away.

No fuse or battery disconnect will clear it.

Most auto part stores can also clear it, Auto Zone, Pep Boys, Etc.

Or any Diablo tuner can clear it or apps are available for phone or tablet (have to buy the OBD-II connector).
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Old 12-07-2015, 05:49 PM
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Re: Thermostat rationality

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Originally Posted by lastchance View Post
I felt like temps were getting to high with the Jet and I was going to just buy another Jet in case mine was faulty but decided to try a different brand 180. Temps were all over the place with the jet and would climb as high as 221* at times when sitting in traffic. The Mishimoto has never gone above 212* so far but seems to hold at 185* most of the time.

Hey last chance

Rehashing an old thread here but I just put the mishi in my 15 and wondering did you bleed the system after install? If so how did you do it?


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Old 12-07-2015, 06:02 PM
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Re: Thermostat rationality

Hey JB, I had a friend of mine put it in for me but I think you just let the engine run with the cap off to get the air out. If I remember correctly he just let it run enough to make sure thermo opened and topped off. Someone else on here will probably give a better answer. Best of luck!
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Old 12-07-2015, 06:09 PM
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Re: Thermostat rationality

Quote:
Originally Posted by lastchance View Post
Hey JB, I had a friend of mine put it in for me but I think you just let the engine run with the cap off to get the air out. If I remember correctly he just let it run enough to make sure thermo opened and topped off. Someone else on here will probably give a better answer. Best of luck!

Thanks mate, that is exactly the advice I've just been given by Mishimoto too. Although I've already driven it to my office (it's morning here) I will let it cool down and try this before I head home later and hopefully does the trick.

Cheers for getting back to me 👍


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