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I have read many threads referring to 203 and 195 degree thermostats. Ford's OEM was the 195 while International used a 203 in their setup of the 7.3. When thermostats are manufactured, there has to be a tolerance + or - some degree or partial degree. I couldn't find out what this tolerance was, but this probably varies by manufacturer. At face value, we are talking about 8 degrees. Does this really make that much of a difference? I would understand higher differences making some changes. If you have some input on this, please respond so we can get to the answer (hopefully) of 1-what does the 203 give you, good or bad and 2-what degree thermostat is the best for the Powerstroke?
 

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Foe some good info on it go to the "supporting vendors" section and click on "Diesel Site" and he has a sticky post(2nd from the top) on it, stating reasons why it's better.
 

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Thanks Rich, that was a lot of information. I would like to find a source of unbiased facts as well. I am not saying that anything was false, but the company would not put anything negative about a product they are selling. There are too many angles dealing with the extra heat that I am thinking of to list, but the question/statement I have is simply put: There must be an engine temperature where the engine operates at the optimum level. Is that 203? The truck needs help (glow plugs) to get going when cold, but will operate at lower temperatures, especially those who have harsh winters. Lastly, does this imply hotter is better meaning why stop at 203? Somewhere that magical 212 number is very close. I know coolant raises the boiling point as well as lowers the freezing point of the liquid used in the cooling system.
 

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I've got the 203 in my truck now and can't tell a difference.
 

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I was paying close attention to my truck's MPG before I installed the 203º thermostat. I couldn't tell any difference in MPG after I added it.

That's not to say the 203º thermostat is snake oil, not at all. I put it into a pot of boiling water with a Murray 195º, and there was a clear difference when they opened. At a full boil, the Murray 195º was fully open, while the 203º barely cracked open.

Does it make my engine hotter? Absolutely.
Does it make a difference? Not that I can tell with my meager means of measurement.
 

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I put it into a pot of boiling water with a Murray 195º, and there was a clear difference when they opened. At a full boil, the Murray 195º was fully open, while the 203º barely cracked open.
At a full boil shouldn't the 203 degree be fully open also, water boils at 212 or something like that.
 

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I think that you will see the real difference up in the cold weather country.
 

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At a full boil shouldn't the 203 degree be fully open also, water boils at 212 or something like that.
Boiling temp. depends on altitude/pressure too. At 5000 feet water boils at ~202.9, so depending on where in NC txgp17 is, water may have a significant lower boiling temp.
 

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At a full boil shouldn't the 203 degree be fully open also, water boils at 212 or something like that.
It should, but I'm betting that the entire pot of water wasn't at 212º, maybe just the water touching the bottom of the pot.
Boiling temp. depends on altitude/pressure too. At 5000 feet water boils at ~202.9, so depending on where in NC txgp17 is, water may have a significant lower boiling temp.
I'm about 800 ft above sea level. And it was tap water, not distilled water. All these variable come into play just a little.
 

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I have the 203 in my truck for the first winter season. I also run the Evan's coolant.

The heat is no doubt much better than with the stock unit.
Does the truck run any better ???????????

I'll add this, with the Evan's being no boil, bla, bla, bla, will this effect the propose of the 203 ???????
 

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I've been running a 203 in mine and everything is fine and dandy until towing.

When towing, such as across western OK during summer, the fan want's to run almost constantly and sometimes seems to cycle on and off. I can't see where if my fan locking up would be saving or helping anything. Sounds like a jet engine taking off when that thing is locked up.

Wish I would've thrown my old one in a drawer and saved it. I'll be buying a new one soon.
 

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Mishimoto is now advertising a 205°F thermostat for 7.3's. What's kewl is they're using the same style gasket found on OEM Motorcraft thermostats that encapsulates the rim of the thermostat. Unlike the more prevalent (and very prone to leak) top-side only gasket.
Ford 7.3L Powerstroke High-Temperature Thermostat, 1996–2003, by Mishimoto

BTW, I just replaced my old 203° with a new 203°. What a total pain in the posterior it is to get it to NOT leak. I had an older Dieselsite billet housing, and it leaked with every gasket I used, including a OEM FoMoCo, Dieselsite, Oreilly. Even hit a parts house and tried a this rubber o-ring.

Finally I contacted Dieselsite and explained my problem. They stated they'd updated they're billet housing. So I bought the updated on and now I have no more leaks.

What still kills me is how long it takes for my 7.3 to warm up. You have to drive at highway speeds for about 8 minutes to get it to reach operating temperature. My personal truck is a 2002 F250, CCLB, 4x4, manual transmission, 3.73 gears.

But my work truck is a 2000 F550, CCLB, 4x4, with an automatic, and in freezing weather, it'll be flowing hot air out the vents in less than 2 miles of driving, and hits operating temp real soon after that. But the EBPV stays on for ages it seems.
 

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Mishimoto is now advertising a 205°F thermostat for 7.3's. What's kewl is they're using the same style gasket found on OEM Motorcraft thermostats that encapsulates the rim of the thermostat. Unlike the more prevalent (and very prone to leak) top-side only gasket.
Ford 7.3L Powerstroke High-Temperature Thermostat, 1996–2003, by Mishimoto

BTW, I just replaced my old 203° with a new 203°. What a total pain in the posterior it is to get it to NOT leak. I had an older Dieselsite billet housing, and it leaked with every gasket I used, including a OEM FoMoCo, Dieselsite, Oreilly. Even hit a parts house and tried a this rubber o-ring.

Finally I contacted Dieselsite and explained my problem. They stated they'd updated they're billet housing. So I bought the updated on and now I have no more leaks.

What still kills me is how long it takes for my 7.3 to warm up. You have to drive at highway speeds for about 8 minutes to get it to reach operating temperature. My personal truck is a 2002 F250, CCLB, 4x4, manual transmission, 3.73 gears.

But my work truck is a 2000 F550, CCLB, 4x4, with an automatic, and in freezing weather, it'll be flowing hot air out the vents in less than 2 miles of driving, and hits operating temp real soon after that. But the EBPV stays on for ages it seems.
Same here on mine it takes like 8min to get any warm air, Mine runs real cool I don't know yet how cool since I need gauge other then my scan gauge but im very interested to what it runs at.

Back to topic - I wouldn't run hotter one personally I rather have it run little cooler. Besides im sure there is reason some ford guy that designed truck and makes 100k+ year decided to do that even with international having different spec.
 

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The guys fixing the engineers mistakes can crack six figures but Ford is pretty tight with their engineers. Adam Gryglak( lead 6.7 engineer) left the Powerstroke division in a Festiva.
 

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I've got the 203 in my truck now and can't tell a difference.
Yep, you are correct. One thing you will get is warmer cab heat. The other thing is elevated EOTs. This should be gauged to keep an eye on this.

ButchCassidy1
 

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I wouldn't run hotter one personally I rather have it run little cooler. Besides im sure there is reason some ford guy that designed truck and makes 100k+ year decided to do that even with international having different spec.
As I understand it, FoMoCo chose the lower temperature thermostat to better control emissions. The pickups faced stricter emissions requirements than did heavier trucks at the time.
 

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As I understand it, FoMoCo chose the lower temperature thermostat to better control emissions. The pickups faced stricter emissions requirements than did heavier trucks at the time.
Exactly. Higher temperatures = higher NOx emissions. The Medium Duty and Heavy Duty trucks aren't saddled with the regulations that the lighter trucks are.
 
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