Moose400ex

good write up! i did my tstat and gasket and wasnt sure which way the tstat went in. it will go in both ways so be careful, and so will the seal. also, i found a shortcut rather than taking off the alt and belt, just undo the upper alt bracket and rotate it out of the way!

nolafishr

Good write up, I just changed out my thermostat but it only has one jingle hole not two, Do you have that part number for the Cummins T-Stat? I may need to change it out if this one gives me problems.

Chrisreyn

Sorry, I dont, however your local dealer or parts shop should have it.

cougar

And the magic number is,,,,,,,
3972071 and the gasket is 3923331.
The previous one I bought from Dodge looked exactly the same.

Chrisreyn

Thanks Cougar! Omitting part numbers was a mistake when I first wrote this..

CactusPete

It is an ingenius design. I've never seen or heard of another one like it that does not use sealer.

cougar

You don't use sealer???

CactusPete

No man, it's designed to be put together dry. Doesn't leak a drop since I replaced it 6 mos ago

cougar

Mine leaks if I don't. The surface is pretty rough.

rebar

I'm wondering if I need a new thermostat.
I picked up a E350 w/1st gen in 80 degree weather and it ran in the lower "normal" range. Ford van gauges don't have numbers.
When I drove the van back up to 40 degree Iowa, the engine temp barely reaches the "normal" range. Im guessing the stat never opens since I'm not towing? or stuck?

When I owned a CRD jeep, I was told I was loosing mpg when the thermostat ran cold. Would that also apply to my 1st gen cummins?

BTW. Mt dodge dealer gave me the stat # of MD972903 which included the gasket.

cougar

That is about were both of mine range, except on a hot day towing through the mountains. Then it will climb to mid way or a bit higher.

BILTIT

Never opens or is always open? Could be either.

I replaced mine and i can see it warm up to the second line then the tstat opens and it will drop down. It will slowly come up to just above the first line i think when it has reached a steady temp.

rebar

Not sure.. My temp does not fluctuate and it takes forever to barely creep into the normal range. And it runs allot colder here in Iowa.
I think the stat is stuck, or I never pushed the amount of fuel needed to warm up?

All I know is it should run warmer but if the fix is a piece of cardboard, I don't want to replace it since the PO said it was new and running cooler than the old stat. But its all hear say..

BILTIT

I would guess it is stuck open. I would replace it myself, or atleast pull it out and test it in boiling water.

thechoochlyman

The easiest way to tell is to get out and check the temp of the radiator when the engine has been running for long enough that it's warm, but not up to operating temp. If the radiator is about the same temperature as the engine, then the stat is stuck open. That was my big problem. After I replaced it, the radiator stayed ice cold until it got completely warm.