Engine/Transmission (1994 - 1998) thermostat question?

[mnick]

DPasho, thanks for the tip on the 440 t-stat. Installed mine and it works great and only $9. 95 from NAPA Mike

 

[RPosey]

Thermostat cycling

The original which came in my truck did not have the rubber sleeve around it and it failed at around 90000 miles. I replaced it with the so called updated one which had a rubber sleeve around it. It stopped the large swing, but it failed pretty quick. I replaced it again, which also prematurely failed. I then took it out and removed the rubber sleeve, which was holding it open, it now works, but with the swing. The repaired one has about 130000 miles, still works.

 

[GOTSOOT]

engine temps should not swing!holding a true temp is prefered for the wearing of the block. expansion and contraction in my opinion is not how the T-stat was designed to work. autos don`t swing,tractors don`t swing,Nascars surely don`t swing. I ha d a non swinging T-stat and replaced it when I had the red. boiled out and have not been able to find it. I have had two replacements, and they both swing. I am goin for the "440"

 

[Joe G.]

Comparing a cooling system with as much coolant as we have in our Dodges to an automobile cooling system that has a fraction of that coolant does not work. The block expansion and contraction idea does not work either. Just going over a hill makes a lot bigger temperature change near the cylinders than a coolant temp change. Or for that matter, just acceleration and deceleration also cause more of a temp change near the cylinders. It's only 40° to 50° change in the coolant temp when the t-stat cycles. That does not reflect the change in the iron. These trucks last a very long time with this so called problem.

 

[Canadian Cummins]

There was a post on here a couple of years ago on this very problem.
The Cummins T-stat sits a little ways from its by pass tube, used to keep a flow over the water pump and not cause any cavitation on the pump vanes.
A quick solution to the problem is to let a small flow of the heated water pass by the pellet in the T-stat, it does not have to be much but keeps the T-stat from swinging. As was described in the previous thread just drill a #40 hole through the t-stat valve as close to the center as possible. I did this about 3 years ago and it sure changed the massive swings, yes it will swing when pulling grades, but no where near as bad as it used to be. This can be done on any t-stat you have.
In face if you look at some import cars they already have a hole in the t-stat just for this.
Hope this helps you guys that don't like what you see when the gauge starts to swing!!!
CC

 

[BigPapa]

... in my opinion...

Here-in lays the rub.



Scott

 

[GOTSOOT]

You all can swing if you want to-not me!

 

[SStryker]

Hi does anyone have the Part number for a 180 degree fan clutch spring. My understanding is that dodge made one to turn fan on earlier which is my problem when heavy towing? Fan doesn't come on soon enough to keep truck cool. Thank You

 

[WDixon27]

i got one of those turds 3 years ago and it ran my engine hot in the summer and cold in the winter up till last week when in installed one of these, it actually works like it should, less then 3 miles into my drive to work it is up to 180 and it stays there, a good portion of the time i could make it all of the way to work and it still wouldn't be up (16 miles of interstate 4 streets) and when running on the interstate with the ac on unloaded it would run 210 or more (with a new radiator and fan clutch) it would come down at lower speeds and to get any heat in below 45* temps id run a insert to block 70-80% of the radiator, i tried a robertshaw from the parts store and it made it run even hotter on the interstate at maybe 220, the mr gasket from jegs was around 22 delivered with the 9 and change handling fee, i guess if i had ordered something else id of made the free s/h that i have gotten in the past on big orders

and the "slow cycling" one is 3934373. both are 180*F.

 

[HCannon]

If you have a cycle problem you arnt loaded. These motors are built to pull. If you are pulling the dog out of it it wont get hot but the cycle will go away. I know, I dont like the cycling when I am not pulling but it is great to load up and not have a problem heating. Just a thought.

 

[Extreme1]

Funny how these old "problems" get recycled periodicly.



I replced my swinging T-stat with a non-swinger years ago on the road. I think I put a NAPA stat in and now it runs steady on the cool side (just above 160). I miss the swinger!

 

[Ramtuf1]

Can anyone identify this gasket

Friend of mine had same problem with temperature and when removing the original thermostat, found a rubber type material lodged in the thermostat holding it from cycling thus causing the temperature issue. I have included a picture (attachment) with the pieces at the bottom with arrows to each. It appears that they are a circular gasket or something if you match up the tears.



Is this a gasket in an original installation as this is the first time the thermostat has been removed?



PLEASE HELP and perhaps explain the purpose of this gasket if it is such as the replacement had no such gasket. If not, any ideas where it came from...



Thanks in advance for the help



Mike

 

[Shadrach]

That is the rubber that goes around the Cummins stat. It is called a "soft seat stat" and was designed to help the stat seal to prevent seepage and therefore poor warm up in cold weather. Unfortuantly it sometimes comes off and get caught in the stat causing it to stick open. If you want to replace it with a "hard seat stat" you could order Cummins p/n 3864178. It is a different design with a hard seat on the inside of the stat. It's only a few bucks more and you will still need the two rubbers p/n 3925466 and 3927305. Shadrach

 

[Ramtuf1]

Appreciate the help with my friends situation. The thermostat that he reinstalled was a NAPA and it didn't have any such gasket included with it so at that point, He was wondering if the gasket was from some other part of the cooling system



Is it necessary to have that circular type gasket? I forwarded him the link to this thread so he has reference to the Cummings part numbers. So I'll let him decide if he wants/nees to install an OEM type stat but he can also see how it performs on the road.



Thanks again for the help.

 

[Shadrach]

The two "gaskets" into the top of your picture, the one to the left and the one to the right of the stat , are necessary to seal the stat. The one that is torn in two, with the arrows pointing to it, was glued to the stat and has come off.



BTY Cummins had no "g".

Shadrach