A few days ago, Saturday I believe, after normally running between 175 and 205 degrees, my temp gauge began only reading up to a max of about 155 degrees. Either I have a stuck open thermostat or the gauge/sender broke.

This '01 has about 178000 miles. I can't get a new thermostat until payday, if that is the problem. I was thinking of taking the t'stat out and flushing it with water to get it "unstuck" though I don't know if this is a good idea.

Any advice would be much appreciated!

Ted

 

Sounds like the t-stat has gone bad. After 180k miles the spring has probably weakened.

 

Sounds like the t-stat is either stuck open or the spring is too weak to keep it closed. Mine died around 165K because of a weak spring. Looked fine when it was removed, but there was no pressure from the spring.

On the bright side, at least it failed open instead of failing partially closed. You can run around with the open t-stat for a little while, it just won't ever get up to operating temp unless you're working it. You could pull it to see what happened, but if it's a weak spring, there isn't much you can do but replace it.

 

Thanks! I'll probably have a look at it, but will plan on getting a new thermostat soon. Like you said, the thing is probably just worn out after opening and closing so many times in these last 178,000 miles!

I just spoke to the Cummins dealer and he asked for my engine serial #. I guess he needs this to get the exact part number and whether it is a 180 degree or 190 degree t'stat.

Ted

 

The Cummins part number for the 180* t-stat is 3967195.

 

I believe the 2001.5 model year trucks came with a 190° t-stat.

 

If you decide to take the old one out, before you try to clean it. Toss it in one of your wifes pans, fill it with enough water to cover the thermostat, put a meat thermometer in the pan and heat it to a boil, watch to see if it opens and closes at the tempature stamped on the thermostat. If it does...its good, if it dosent, toss it and buy a new one.

 

Thanks everyone. This is good information.

Just in case I need it, I now know the 180 degree part number. Does anyone have the 190 degree p/n?

Ted

 

Don't bother using one. The 190* tstat is a Dodge thing designed for faster warm-ups and they're garbage. Stick with the Cummins designed t-stat and be done with it.

 

I'm looking at a replacement 190° t-stat that I bought two or three years ago at the local Dodge dealership. I haven't used it yet. It's in a Cummins box with the Mopar label on it. The Cummins p/n is 3946849. The Mopar # is 05015708AC. You had better get ready for price sticker shock. Also, the new t-stat doesn't look anything like the old ones - totally different design. The new ones are supposed to correct the design flaws in the older models or so I've been told.

 

The 190 thermostat works fine. It is better suited to your truck because the fan hub locks up at about 206 degrees. This limits the temp cycling to about 16 degrees instead of the 26 you would get with a 180 and heavy loading. Less engine wear is the result and it will also run cleaner and give slightly better mileage.

If your engine will no longer come up to temperature the thermostat has failed. They are designed to fail open rather than closed.

 

Excellent information WestTN. I appreciate the help. I am all for less engine wear!

Ted

 

Go with the 190 for an 01.5. I researched this and the newer 24v's like to run a little hotter.

IIRC the gauge will point all the way to the right if the sender is bad.

Kurt

 

Thanks KurtainG, this is good information.

I have noticed the tendency to run slightly hotter in my 01.5 than, say, either of my '97 12 valves. Those trucks would always swing widely between 170 - 190 degrees, while the 01.5 will run as hot as 205 before the thermostat opens and doesn't have as much variation in temps.

I think the local Cummins dealer will probably recommend the 190* anyway after I pass my engine serial # to him.


Ted