I have been fighting an overheating problem on my non-intercooled first gen (early 1991). I am at the point of changing the thermostat.
I picked one up at the Cummins dealer. It looks like the wrong one. No bypass valve disc at the end of it.
The Cummins parts guy swears that this one replaces the old one. Gave him the engine # and he sticks to his story. The one he gave me is Cummins part #3972071.
Does anyone know anything about this?. The part # i was wanting was 3802273. The new one doesn't look like it closes the bypass in any way. Of course it's Friday and I need to get this resolved so I can get to work. RIght now it is all apart.
Any help or insight would be appreciated.
-Bill-

 

If it doesn't have the bypass disc it's wrong - do not use it!