My 2014 with 70k miles has the error code for low coolant temperature so I plan to change the thermostat soon. I'm wondering if you would advise to do a coolant flush, or simply just top it off after replacing the t-stat.

 

If the coolant has been in the engine for more than a few years, I would flush it. I have been flushing mine every 4 years.

Have you checked the engine temp with an IR temp gun? Could be the temp sensor isn't reading accurately.

 

Auto correct, I don't want to fish. What I see when using the elm OBD reader is that the coolant temp reads to be around 183 degrees on a 100 mile highway trip. This agrees closely with the temp I see in the EVIC on the dash. The error code started as intermittent. I would reset and it would stay off for a couple of weeks. Now it is on and my code reader won't let me reset it

 

I'd change the thermostat and top off. That is 150k mile coolant in there. If it was 100k mile HOAT then I'd agree with ronjenx. If you were doing a bigger job like a whole radiator then I'd agree as well, but for the bit you're going to lose doing the thermostat, just top it off.


I fixed it

 

Haha,the two guys in here I respect most giving me opposite advice! I need a tie breaker.
I think I'll evaluate the appearance of the fluid and the condition of the internals I can see during the replacement job and make my decision then.

 

Just flush and change. It's cheap enough to do it. If it's never been done before, you have 8 year old coolant, and it's close enough to change it. Plus you will know what's in there for a fact, incase the previous owner topped it off with a universal coolant.

 

IMO.. Flush at time of repair seems logical.. only 70K on the 150K coolant leads me to go with replace t-stat and top back off.. Either way you are going to be "Burping". Have you priced the superceeded Mopar coolant? I go with concentrate and use distilled H2O.

 

Believe it or not I give my coolant the taste test - literally!! If it is sweet then it is still good, if it is going away towards sour then change it. Hasn't killed me yet but I am not stupid enough to swallow it. When it is souring it is going acidic.

 

I used to have an electronics classroom text book from 100 or so years ago. There was a chart that showed how to determine voltages by touching the wires to your tongue. Different voltages produce different salts with unique tastes. I assume it was for telephone/telegraph voltages. Right up there with tasting antifreeze.

And I found the mopar concentrate on Amazon for around $29.

 

I just had a problem with my thermostat housing and I'm replacing the housing, thermostat, upper and lower hoses plus a flush. Overkill for sure but I have an Airlift which makes it super easy to do a flush. It's not a true flush so keep that in mind. But I end up getting about 2 gallons in and out of the system each time you do it. My vote would be for a flush. I pull the lower hose and put new coolant in before my summer Baja adventures. Plus the cheater transmission fluid swap also.