Hey all!

I've recently installed the International water pump for our trucks with the filter and changed to the 203* thermostat. I am now seeing sustained oil temps of 217* with no load, regular driving and ambient air temps of 90*ish.

I've read all the high oil temp threads on here and understand that 217* isn't out of the norm (I used to run 195*-210*). But I did come across the idea that the 203* thermostat might not be the ideal one for our trucks and that the 195* is the better one to run with.

So my question is; which thermostat to use, the 195* or the 203*?

Thanks for any input!

 

If I may...

I too switched to the IH water pump with the 203° thermostat and saw similar temperature increases like you did. I did a lot of research and found out the increase up from the 195° thermostat is negligible and how the engine was designed to run by International.

You can actually get a short stem thermostat for the IH pump all the way down to 182° I think, maybe it was 185°.

I saw temperatures near 220 and 225 occassionally when running the truck hard in the dead heat of summer, but again those temperatures are nothing to be concerned about. Keep an eye on it if you like, but the temperature is safe to run in that range. Now if it started to get up to 250°, I would consider looking at possible problem areas. Even then, synthetic diesel oils like 5w40 and 15w40 are safely rated for higher than that.

There is quite a bit if information and discussion on this topic, but I have summed it up for you for the most part.

 

Your not alone with being discouraged with the 203*. Tons of threads about the same situation. They reverted back to 195*

 

I threw in a 203 with a new water pump a couple years ago and have never had oil temp problems. In chillier weather it will stay below 200 and in hot weather towing heavy I have briefly seen it hit high 220’s before settling back down to mid 210’s or lower when the road flattens out. I don’t think it makes that big of a difference honestly with how efficient the cooling system is on that engine.

 

Thanks guys. I'll watch it for the time being and if I don't like what I see I'll switch back.

 

James, if you decide to switch back, be sure to remember that the stem for the thermostat in the IH water pump is NOT the same size as the OEM/Motorcraft water pump.

I have a couple of part #'s noted on my "7.3 Wish List" of parts and they are as follows.

481828 or 1845804C2 or 1845804C1

 

I had the hotter thermo on my Ex and I didn't like it. I pulled it and went back to OEM from Ford.

I had the OEM thermo from Ford on my '99 with dual Terminator HPOS and had to swap it out for the Termy made 180* because of the extra heat the dual pumps created.

Previous thread for more info: https://www.ford-trucks.com/forums/1...l#post10768402

Stewart

 

@Stewart_H did you not like it because of the 10-20 degree increase in temperature or were there other reasons behind the decision to go back to ~195 thermostat?

Do you suspect that had an impact on your recent coolant leak/head mystery recently?

 

I should have qualified my statement, because I was not stock, and I should have included that info.

Why I changed back to a Ford OEM 7.3L thermo was due to the extra heat that grew to more than I was comfortable with when I was towing our travel trailer, or in weather with high temps while unloaded.

As for if it contributed, who knows. I understood I was shortening the life on my engine when I started modding it. Sure, I thought it would last longer than it did, but I went in with eyes wide open.

Stewart

 

Could also be that their old trucks needed the oil cooler rebuilt because it was plugged up and running the temp up. These 7.3 have a way over
built cooling system, if anything gets even close to hot there is usually something mechanically wrong.

International has built a ton of these motors in every thing you can think of, and I bet they are all at 203-deg. I would think that they
know better where the motor should be running than us (or Ford) guessing where it might be better. Cooler isnt always better.

Could be that Ford had a temp sensor that worked better 8-deg cooler and it was cheaper to just use a different thermostat than design
a new sensor. Engine just had to last 100K miles so go for it.

My truck had a broke thermostat I found when changing out the old water pump, so this isnt a great comparison.. BUT.. With the new pump and the
203 it has much more power, is more quiet, lower EGT, and gained 2-MPG. This from just getting the engine heated up. Now the temp gauge always
read fine and the heater blew good heat. That old thermostat was broken for years as the truck hasent gotten great milage for as long as I can remember and
has been, noisy especially in winter, for a real long time.

 

I just got back from a 200 mile trip over flat land/rolling hills, towing a new trailer that weighed in at 9200. I saw oil temps of around 225 going 68-70 mph with an ambient temp of 84. Went down to about 215 when i got my speed down to 60. I rarely saw over 220 EOT while towing 7800. I suspect the truck is just showing its age, but I really like the 203 thermostat in the cold weather.

 

It might sound like a statement from a Patton patient but,
i recall reading how the t444e equiped in street sweepers came equipped with a 203* to keep heat up, help atomize the fuel since rpms werent there..etc, and thats how the 203* came to light for our trucks so, members ran with the idea..