My 01 with 47re has started running cooler than normal its always ran 180
or a hands width below give or take, unless hauling then it would go past maybe 1/8 of a inch then back just normal thermostat an engine fan cycleing
stuff . Now normal seems to be halfway between cold an 180 . I hauled a tractor last night outside temp about 65 an it would climb to 180 on long pulls
then go right back to half way between cold an 180 . My engine fan seems ok
I did not hear it kick in an I raised the hood with engine off an by hand it turned with very little resistance . So am I pretty safe in thinking I,ve got a sticking thermostat ? This truck has 150000 mi on it an i,m guessing that is the original although I did change the Anti Freeze when I bought it at 130000 mi . An do these trucks call for a 180 degree stat ? The only other thing I can think of is a bad Temp sending unit or radiator cap . I can check the cap but don,t know how to check the sending unit .
Thanks
George

 

Start by confirming that temp on gauge matches actual radiator temp. Use a $3 meat thermometer if you don't have one of the fancy schmancy $15 gauge from Harbor Freight. If the 2 match, sending unit is good.

IF you need a TStat, get a Cummins. The aftermarkets let the temp cycle up & down & are a waste of install time. They are good for scavenging the gasket before returning to store for refund. You could boil you current stat & see where it opens.

 

Ok sounds like a plan these 01's did take a 180 don't they . I've got access to a infared gun , but something I could actually stick into the coolant proubly would give a more accurate reading I'd think ?
Thanks for the input junk Man .

 

The 01's take a 190.

 

Bad thermostat is most likely the cause. Mine did the same thing too but it wasn't quite so cool. I've heard that you have to be careful where you get a new thermostat too. Some will even tell you to stay with OEM because over the counter stuff is garbage. I got mine at NAPA and it works great. I checked and it seemed to be the same quality and size opening as the OEM one.

 

Sixslug I see yours is a six speed would the Auto take the same Stat ? Thanks guys I'll dig into this tommorrow . I'm sure the parts man will ask me if theres a difference i'll call the local cummins
distribitor or Dodge .

 

Cummins is less expensive than the dealer. Local truck shop may be less expensive than Cummins. I usually call Cummins for part # & inventory then have Rush (truck repair place) order & pick it up for me. Rush is open all night.

 

My service manual shows a range of 181F-203F for opening and closing temps regardless of trans.

My inquiry re: the correct stat in the past resulted in a 190F for my 01.5.

 

I put the the oem Cummins Stat in it 190F . Its back to normal now.
It appeared the one i took out was not the original,it was fully closed though I was exspecting it to be partially open .

 

Aftermarket tstats are only good for the gasket in the event that you have an OEM Cummins tstat that needs the gasket. The gaskets become brittle & cause a leak but can be repaired with aftermarket. Gasket is not available alone.

 

mine does not have a gasket, only a O ring