Running too cool

SparkandFire

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So I noticed today while making one of many runs up the mountain to move all our stuff into a new house, that my temp gauge was really, really low. normally it warms right up to the "N" in normal...

I know better than to trust the factory gauge, but I haven't had the time to add one on yet.

I turned the heat on full blast and it was barely lukewarm. Pulled over and checked the coolant, both upper and lower hose were warm but not hot, pulled the cap off and it was full of coolant, no bubbles or anything like that.

Is my thermostat stuck open??? Is it ok to pull the Uhaul trailer up to 3800 ft elevation tomorrow with the truck?? :dunno
 

Brianedwardss

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I once worked for a fleet that had 72 freightliners with Detroit 60-series engines, and in the summer they had me remove the thermostats on all of 'em. Worked there four years doing that three summers in a row. I had the thermostat stuck open on my '90 7.3L idi for probably 6 months. It never caused any issues. I figured a stuck open thermostat still provides enough restriction to keep it somewhat warm, better than not having one at all, or it being stuck shut. I've heard an open thermostat can cause hot spots and un-even cooling. I think that applies more for folks doing alot of idling. Towing, your engine will be opening the thermostat anyway, so I see less of a problem.
 

turbodiesel94

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When I first bought my truck my tstat was stuck open, upon removing it we found that someone had let a piece of hose clamp in my water system and luckily the tstat caught it before the water pump did. But while driving it while it was stuck open I only got 10-12mpg, with it functioning properly i jumped up to 16-18.
 

icanfixall

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Every idi block has a bypass coolant system in it... When you remove the factroy thermostat look into the block. There is a bump with a hole in it. Now lok at the bottom side of the factory only thermostat. See the large copper pill... Well as the thermostat opens it slides down into that hole and blocks off the bypass of coolant that flows directly to the water pump. This is why we use only the factory thermostats. I know some members are running after market stants without any issues but... I'm not going to try to explain just how they are getting away with that. With our engines we can run a part that isn't factory... The thermostat isn't one of those parts. The oem works and has worked fine for many years... If something else came along we as a collective would be running it now. This forum has a wide base for testing things and knowing what does and does not work.... When I remove a thermostat for whatever reason I test it in a pot of boiling water. These stats must open a minum of .026... Thats a the full open temp. There is another measurement too. At full open temp measure from the bottom block side of the lip that seats in the block down to the copper pill bottom. At full open it will measure 1.19 inches. If I recall correctly that shows around a .250 opening between the two parts of the thremostat. That rubber gasket that glued to the body og the stat is there to seal the metal to metal seat on the closed stat. I usually cut off the part at the seat so I get more flow at wide open settings... Works for me....
 

FORDF250HDXLT

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When I first bought my truck my tstat was stuck open, upon removing it we found that someone had let a piece of hose clamp in my water system and luckily the tstat caught it before the water pump did. But while driving it while it was stuck open I only got 10-12mpg, with it functioning properly i jumped up to 16-18.

yeah.so many people think diesels are like gas engines,in that the cooler the better.
this simply isn't so burning diesel fuel.

a real aftermarket gauge is really important.
these IDI's run most efficient at that their normal operating temps of 212-237 degrees.
i just switched to dual ford windstar fans,run the stock motorcraft 192 degree T-stat (thats fully open around 210-212) and try and keep my temp at anything over 210 and under 240.
when i dont have the plow on,i turn my fan control so that it doesnt turn on until 225 degrees,so im not forcing the T-stat to open and close,open and close.rather than fight the normal operating temp,i just keep it so it doesn't go out of the range on the high side.just make sure i stay under 240,and life seems good.:)
the powerstroke guys learned going to slightly higher T-stat helps them 203 degree i guess it is.

a lot of people don't realize its just as bad to over cool a trans or engine,or any other part of the drive train.
everything has a sweet spot for max performance and efficiency.;Sweet

SparkandFire,
i wouldn't worry too much.you wont hurt anything hauling or even just driving around.your mileage might suck,and you may not be to warm in the cab,but id do what i needed and then replace the T-stat when i had the time.
for now,until you replace it,grab a piece of cardboard and cover half of the rad.watch your temps!
if you see your stock gauge going outside the normal from where it runs,reduce the amount of cardboard.this will bring the efficiency of the engine up for ya,and give ya a little heat in the cab for now.be prepared to pull over and remove it all together once you start pulling some grades and work the engine though.use caution.
stuck closed.well that would be different of course.she'd be parked until it got replaced.
hope that helps.
 
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Silver Burner

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I need to check this because I don't necessarily trust the dummy gauge, but it never reads above the first line to normal and I only seem to get about 12-13 in the city. It jumps to close to 18 on the highway though, so weird...
 

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