Engine/Transmission (1998.5 - 2002) Thermostat choice

[FLynes]

I see that we have a choice of 180* or 190* thermostats... which one is stock, and which one is the best choice?

 

[WestTN]

190 is stock and also my choice for all situations. The thermostat opens at 190 and the fan clutch locks up at about 206. That means the engine temperature can vary about 16 degrees. With a 180, it is 26 degrees.



The more the temperature swings, the more engine wear you get.

 

[FLynes]

Gotcha, thanks Dennis.

 

[Vaughn MacKenzie]

190 is stock and also my choice for all situations. The thermostat opens at 190 and the fan clutch locks up at about 206. That means the engine temperature can vary about 16 degrees. With a 180, it is 26 degrees.

The more the temperature swings, the more engine wear you get.

Kicking this thread up because I am thinking about switching out for a 180F thermostat. As to temp fluctuations I would argue that with a 190F T-stat you are putting the engine through a wider heating/cooling temp range every day going from start temp to operating temp. Especially people like me who abuse their Cummins and take short trips And even more so during the winter when the temperature range between ambient and operating temp is very wide.

How do 12-valve engines last a million miles with their temps fluctuating incessantly between 150 and 190 all day long? My '96 12v fluctuates wildly, it makes the full swing every couple of miles. . . somehow that temp gauge needle hasn't fallen off after 438,000 miles

I would also argue that in theory an engine operating at 180F should last longer than one at 190F since it puts less thermal stress on engine components and lubricating oil.

Some food for thought anyway

ps anyone know the Cummins part number for the 180F thermostat?

 

[Crazy Horse]

As of Dec 2009 the latest part # for the 180 deg thermostat for the 2002 Cummins is Cummins #3967195.
And I agree with you:

I would also argue that in theory an engine operating at 180F should last longer than one at 190F since it puts less thermal stress on engine components and lubricating oil.

I've been running the 180 since 2005.

 

[Vaughn MacKenzie]

Thank you Crazy Horse.



I see Geno's sells 180F thermostats but they are Gates brand, don't know how good those are but it's interesting they sell those instead of Cummins'.

 

[SHobbs]

I found both online and the 180F is half the cost of the 190F. What is so special about the 190F?



1998. 5-2002 Cummins 24 Valve Parts



Scroll down a little.



Scott

 

[PC12Driver]

A jiggle pin maybe?

 

[barryg41]

I got the Geno's 180F. It runs good. And the temp is steady. It's only been in for six months tho'.



It acts just like my old 190F.

 

[1tuffram]

Anyone know if the thermostat used in the 24 valve engine will fit/work in the 12 valve engines? I have not seen a 12v and 24v engine t-stat side by side to know if they could interchange.

 

[krtcummins]

I installed a 180 in my 01 when I first bought the truck. I installed a new 190 when I serviced the cooling system again this year. With the new 190 thermostat the engine seems to warm up quicker. One would not think ten degrees would make a difference, but it does. The temp guage needle only rose about 1/8" hotter with the 190 thermostat. The engine ran the same on the guage when pulling hills as it did with the 180, so no problem there. I don't know. Seeing as how our engines like heat to run efficiently, I think I will stick with the 190 like my truck originally came with.

 

[jray]

I can remember reading years ago in a Chevy Hi-Performance rebuilding book from GM that lower temp. thermostats actually accelerated the wear of cylinder walls. From what I remember the 160 thermostat radically accelerated cylinder wear. The book was written over thirty years ago and based on what was written, I always run the higher temp thermostats. JMTC.

 

[krtcummins]

I can remember reading years ago in a Chevy Hi-Performance rebuilding book from GM that lower temp. thermostats actually accelerated the wear of cylinder walls. From what I remember the 160 thermostat radically accelerated cylinder wear. The book was written over thirty years ago and based on what was written, I always run the higher temp thermostats. JMTC.

I wasn't going to say anything, but Cummins builds the engine to certain bearing, piston/bore tolerances. The manufacturer specifies a certain heat range thermostat to work with those clearances, as they do a specific weight engine oil. I know gas engines use a 190 thermostat for emissions, but back in the 2nd Gen time running a Diesel engine hotter for emissions was not common practice to my knowledge.



I'm not going to go so far as to say my truck runs better with the 190 thermostat, but it sure warms up way quicker than it did with the 180 thermostat. (And I live in the hot SoCa high desert) I can't believe that would not be better for engine wear than a slower warm up time with a 180 thermostat. It does not matter which thermostat you use, the engine will still run at the same temps when hot pulling hills, Etc.

 

[klcammie]

Thanks for the link. There is a lot of gooooood stuff here.

 

[EdK]

My '99 was 180*

Not to muddy the waters... my '99 came with a 180* in it... HONEST! And yes, I have owned it from day one! I still have it around the shop somewhere as a "backup. "

 

[J.BURCHFIELD]

For what it is worth the shop manual should be your guide as to 190 or 180. the shop manual for my 1998 12v said 180. As for brand I would only use STANT. A Stant will not stick closed. Some will. You know what that means. You can get where you are going stuck open. Stuck closed could mean needing a tow truck.