If you have ECT of 186 and EOT of 194 would changing thermostat tighten that split? ECT should be 190 min. correct?

 

It could, not definite.

 

I wouldn't mess with changing hardware until you're consistently in the 170s. 4* is as likely to be sensor bias as it is to be the t-stat itself. I've been at 188* for several years now.

 

I would change it out just to get the ect into the 190's or above for better operating efficiency and possibly better mileage.

 

I agree. I think my truck runs better when it's warmer. I fought my own small battle with thermostats awhile back. I've changed mine 4 or 5 times trying to find one that would hold. Seems to me they all eventually start creeping down in temp but the Motorcraft ones do seem to last longer. One of the aftermarkets I tried fell below 185° in just a couple weeks!

 

^^^ And that's why I wouldn't bother changing it out yet, odds are the replacement will be roughly in the 186-188* range anyways. Compare cold soak temps and swap the sending units before you do anything else to verify a mechanical concern and not just sensor bias.

 

I was thinking about the changing to get in higher operating range on ECT. I do notice it does run better and with less split when the ECT temp is stays above 190. I guess my other question would be would EOT raise those extra 4* as well ie: follow the ECT? My cold soak temps are dead even on ECT, EOT, and TFT. With 137K on it--I would say it's time to change it anyway more so to get her heated up a bit more IDK.

 

EOT follows the ECT when fully heat saturated. My truck ECT runs consistantly between 197 and 204 depending on ambient and load. There's absolutely no problem with an 8 degree spread. Don't chase rainbows. You'll never catch one.

 

Not chasing rainbows for sure--not worried about my split at all as it is consistent and within spec. I don't necessarily like the coolant temp down in the 180s for efficiency of course.

 

I agree with you 100% on the low temp. I would try a new Motorcraft if it were mine.

 

EOT will go up also

 

Kinda thought so but wasnt sure

 

If you change it out, I'm interested to know if the ECT increases to 190+ or if it turns out to be a sensor bias issue.

 

Will post up when I do it in a few weeks when I change the oil and such. I'm ruling out a sensor as all three temps are the same after 12 hour cold soak and within a degree of ambient so I would say the sensors are calibrated exact I would think. Could be wrong though

 

Its 4* off. 4* will not make any difference at all. And yes, eot will follow.