Low coolant temps?

[BigPapa]

I'm having an unusual issue I just can’t figure out. My coolant temp will hardly ever get over @ 160*. I initially thought my 5 year old thermostat was stuck open so I replaced it Friday with a new Cummins 3928499, no change. I replaced the water pump with a new Cummins Water Pump in October. If it wasn’t pumping I’d think I would see high temps. Both radiator hoses get hot so I don’t think it’s a circulation issue. I lasered the thermostat housing after driving 40 miles and it showed 168*. I’d say I have a sensor or gauge issue but my transmission temps are low, too, and read the same as my ECTs.

Ambient temps in the lower 90’s, high humidity. City traffic and interstate driving empty. Fan clutch is functioning properly.

Tell me what you think.

 

[ofelas]

I didn't see this post here until a minute back, but I replied to you on that other forum.

I'll repeat it here for anyone else who may run into a smilier issue -

"The # 3924489 you referenced is an oil pan.

Unless you mistakenly meant to type out "Cummins 3946849"
which is a 58mm 24v stat with the perimeter seal - it will let coolant past even when closed, causing a cold operating condition on a 12v.

The 63mm 12v second gen stat you need is # Cummins 3928499, with inner & outer seals # 3925466 & 3927305."

I initially thought my 5 year old thermostat was stuck open so I replaced it Friday with a new Cummins 3924489, no change.

 

[BigPapa]

You got me.

I corrected the post, 3928499. It's the correct thermostat for my engine.

 

[ofelas]

Pull it & check if the rubber shroud got loose & stuck in the opening, keeping the stat open.

I've seen that a couple times.