Engine/Transmission (1998.5 - 2002) Defective t-stat...thought I'd share...

[rotohead]

I mentioned this on another thread about coolant and someone emailed me about what I found when doing a coolant, t-stat and water pump servicing.

This is a standard t-stat purchased six or seven years ago from a Cummins parts dept. For the past few years noticed it took a long time to come up to operating temp but since I drive five miles downhill when cold it didn't get my attention until lately.

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The round, flat stopper was wedged in a corner of the cooling passage... glad it didn't work it's way down into the engine any further. With my luck it could've really been a problem and hard as heck to troubleshoot and remove.

The last pic shows the NAPA box with a drawing of a different style tstat. I wish I had taken a pic before installing but the drawing shows a brass 'plug' type that I liked better. Part # on box is 375-190.

Something to look for when doing coolant changes is how that round, flat stopper is attached to the center stem. It's just stamped on there much like you stamp a rivet or brass snap. Very flimsy IMO. Hope the pics come through.

Chuck

 

[2broke2smoke]

great post, thanks



i'm getting ready to do the same thing for my '01 ... at 150k



just curious how many miles on yours

 

[FLynes]

Thanks for the info, rotohead. Am I to understand that this is an OEM part that came apart like that?

 

[rotohead]

great post, thanks



i'm getting ready to do the same thing for my '01 ... at 150k



just curious how many miles on yours

I installed the t-stat shown at about 40k mi but it was OEM replacement from Cummins. Found this problem a couple weeks ago at 101K mi while replacing coolant, t-stat, pump, hoses. Maybe this is something to think about when using these 'extended life' coolants like the Texaco 7 year 150,000 mile product. I used that stuff and used test strips last summer to see if I needed to add the extender but it showed well within limits so I just kept going. Last month I decided to change because I wanted to do the hoses at the same time I had vacuum pump/ps pump, alt, boost hoses, all that stuff out so it made for more room. I could've gone longer with the coolant (Texaco stuff is great IMO... looked as good as new when drained). Now I'm wondering if extended coolant pushes other parts past their designed life limits. Since I'm just a DIY mech I don't have the background to know if this is something to be worried about.

Chuck

 

[rotohead]

On the first pic you can see how the center stem of brass had deteriorated on one side to allow the stopper to detach. I think this process took some length of time to happen... many cycles but I also think that the final detach happened just recently. I don't have any other OEM t-stats to compare it to but it seems to me that with the pressure/temp it's subjected to over 70-100k miles... it needs to be a better attachment to the stem then that. I could've replaced it with minimal coolant loss somewhere in the 50k mi range and just given the radiator a shot of distilled water to replenish I guess. Are there other t-stats out there that are different than Cummins or even the NAPA one I show?

Chuck

 

[RSimmons]

The replacement thermostat I bought from the local dealership looked very much like this one for GM http://www.jegs.com/webapp/wcs/stor...tId=752512&itemId=82412&langId=-1&showValue=1



My original appeared to be identical. The thing was almost 50 bucks though.