Engine/Transmission (1994 - 1998) Is this a thermostat problem?

[rha478]

I have a 97 3/4 extended cab 4 X 4 (completely stock except for a straight pipe). I live in East Texas, when it is cold to cool outside (up to about 60 degrees) my truck will not heat up all the way. It shows that it is approx. 150 to 160 degrees. When it warms up outside (above 60+ degrees) it will warm to full operating temperature. I was wandering if it is the thermostat or something else. I would appreciate any feedback.

 

[rrl989]

I had a similar symptom, truck took forever to heat up. Never really heated up at all in the cold. The thermostat had ate part of its gasket, so it was never fully closing. Also, our stats are designed to vary between open and closed, so the flow rate is not just on or off.



Ron

 

[T-Bone]

I had the same symptoms on my 1997. Got a new thermostat, seal and gasket at Cummins. The thermostat below is what I found when I opened things up.



Part numbers used:



Thermostat - 3928499 (this is the “old” part that was superseded by 3934373).

gasket and seal – 3925466 3927305



T-Bone

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[JWilkinson]

Also check overflow valve. Low pressure will keep engine from warming properly.