I just put in a brand new Mishimoto 200* stat, in the Mishimoto housing it came with, in my Excursion because the one I put in 5 years ago kept holding lower and lower temps. It was down to 192 when I took it out. Put in a Motorcraft stat that held 192 for a couple months and then was at 188 or 186. So I got the new Mishimoto and it is holding...190* 🤦‍♂️

 

So what is the solution here? Sean, is your International thermostat holding temperature or is it slowly weakening?

 

Well it's holding 35º right now.
But it is sitting in a box with other parts.
But when it was running I got the best temps out of the IH T-stats and longer than one season.
I think I got more than 4 years out of it. The engine does not build a lot of heat sitting in the driveway
with the wrecked truck. I am almost ready to put plates on it and drive it. When I got the new truck
in July 2017 I put one in it also.

 

My first Mishimoto stat held a perfect 200 for the first 3 1/2 years. Then it started slowly opening up earlier and earlier over the next 2 years. Finally going down to 192 before I removed it. So, so far it is by far the longevity champ in terms of holding temp. But the brand new Mishimoto...well...

I have an International stat that I could try...but that would really only get me to the temp I’m holding right now

 

Both of the IH ones I have ran about 198º~202º on a regular bases.

The one truck that has the engine in I can't take out onto the road yet.
So idling in the driveway does not put that muck load on it. Makes it
hard to reach much over 192º.

 

Interesting...maybe that’s the way I should go.

But first I need to contact Mishimoto and get them to send a replacement under warranty. I should get TWO stats under warranty, but I can’t remember where I bought my first one so I don’t have a record of purchase 🤦‍♂️

 

I can tell you just from the way they handled the T-stat at the start I am not a fan.
Noting like using your customers as beta testers and not telling them. They sent that
thing out without a housing and that caused all sorts of issues for people.

 

That's typical with aftermarket parts, they don't have the resources to do R&D testing on the scale OE does. My old companies aftermarket division relied on warranty returns for correcting issues, and they were better than most other major companies. The smaller companies, the term "hope and change" started somewhere.