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Hey guys,

I just heard something else about this temp debate, that I haven't seen anyone talk about yet... Other than in some of the technical info from 'Diesel Site'.

It was said there, that the 203* thermostat will actually reduce your exhaust gas temperatures.

Is that true? Does anyone have any experience and real world numbers on that?
 

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Hey guys,

I just heard something else about this temp debate, that I haven't seen anyone talk about yet... Other than in some of the technical info from 'Diesel Site'.

It was said there, that the 203* thermostat will actually reduce your exhaust gas temperatures.

Is that true? Does anyone have any experience and real world numbers on that?
The higher the oil temperatures the lower your injector pulsewidth will be (and theoretically lower the exhaust temps), there is an actual map in your programming that does this.
 

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I bought a napa one. Pretty sure it was a mistake anyone have a link to decent one?
 

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I bought a napa one. Pretty sure it was a mistake anyone have a link to decent one?
http://www.dieselsite.com/dieselsite203thermostat.aspx
This is where I got mine and I would buy the billet housing also. I didn't at first but after a nagging leak, I purchased the housing and stopped it.

I am quite happy with my 203 thermostat, I have real heat in my cab now and engine temps are now in the normal range. EOT's are around 198-200 and my truck seems to run better and is a little quieter.
 

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i would just run the stock one.

I have talked to quite a few people who experience puking out the degas bottle running the 203 thermo. They live in hot climates as well.
 

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I'm going to add my two cents to this (debate) and most people won't like it because it's going to be from my usual cynical angle. I think guys selling "mod" parts look for ANYTHING they can find that's a little bit different and then make up stories to support why you should do/get it (the parts). Someone saw that 8 degree difference between the OEM Ford & what International uses and the dollar sign's started flashing in their eyes. To start with, 8 degrees just isn't a hell of a lot of difference in the 200 degree range. With all the variables previously listed (altitude, towing or not, summer or harsh winter conditions, different types of antifreeze & probably the biggest of all....These thermostats just aren't that Damned accurate!), I say if your looking to spend money for nothing & want to spend time wrenching on something that "ain't broke so don't fix it", Go get you a new 203 thermostat & don't forget that fancy billet housing ya just got to have because the stock steel is going to rust in place & you will never get it off in 10 years... blah, blah, blah.... What you have here is nothing more than CLEVER MARKETING! There are plenty of other things that you SHOULD spend money (upgrading) and that DO prove to be a positive benefit to slight design faults. Off the top of my head the fuel crossover mod. is probably 10 times more worth the effort & money to do. That's my 2 cents on the subject. Not looking to argue or debate it. Just putting MY thoughts out there for anyone interested. DDT
 

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Nick, im sure you would have beat me to it if i was any slower haha

A fellow powerstroke enthusiast (csipsd) who cruises other forums and tows all over the west coast had issues with it puking while towing in california. He drives a lot (30-50k) every year and didnt notice any benefit. So ill just save my money
 

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For my nickles worth, I have been running the 203 degree thermostat in my OBS truck now for a couple of years with a couple of long hauls with it. I haven't noticed any difference in mileage, or performance over the stock one. It does get the temperature gauge up to a nice mid range which the stock one never did do even when I was towing heavy with the AC on across the Utah desert in July.

So in my opinion if you want to try it then by all means try it but don't expect miracles
 

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FWIW, when my thermostat fails then I intend to replace it with the 203. I don't know what is currently in mine but in these colder climates I always choose the hottest t-stat option because it makes the heater blow warmer and another advantage is the slighter hotter engine will take just that much longer to cool down giving me that much more advantage when re-starting.

The advantage in cold climates would be similar to the advantage of grill covers in winter.

I am not expecting an increase in fuel economy but I do not see how this will hurt if the commercial 7.3's run them from the factory.

This was an interesting thread.
 

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203 tstat = warmer butt in cold weather, BUT in summer watch for elevated EOT - that could cause cooling issues especially towing.

ButchCassidy1
 

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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.
So Dieselsite made you purchase an upgraded model (at full price, I assume) to replace their defective one??? This is irritating, but helpful. The irritating part: I also have a leaking Dieselsite billet housing that I assumed was the gasket, and now I hear from you that there are no gaskets that will fix it??? The helpful part: at least I've heard about the problem from you and havent spent any time trying different gaskets!!! What about siliconing in a new gasket? Do you think that might work, or is it a bad idea to start with?
 

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So Dieselsite made you purchase an upgraded model (at full price, I assume) to replace their defective one??? This is irritating, but helpful.
Not at full price, no. It was deeply discounted, about 50% off if I recall correctly.

I'm not happy about it either, but I prefer that to a leak. I was sick and tired of seeing leaking coolant from the t-housing. Buying the new design was worth to keep me from snooping around my truck everytime I caught a wiff of coolant.
 

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203 tstat = warmer butt in cold weather, BUT in summer watch for elevated EOT - that could cause cooling issues especially towing.

ButchCassidy1
Thanks :thumbsup:
 

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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?
I had a new water pump and 203 thermostat put in my 7.3. Its noticeably warmer. Don't need the grill cover in the winter anymore. The gauge was always on the colder side and now in the middle. Since then I've had electrical problems with the shifting overdrive off flashing light and hard shifting. Only when its hot. I changed a lot of sensors. I added shielding metal between the exhaust and transmission. There are lots of wires, connections, sensors.. there. Im guessing thats why Ford wanted a cooler temperature originally. The motor almost doesn't fit in the truck. There isn't much room for wires and electrical.
 
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