Georgia Mike Posted January 17, 2022 Share Posted January 17, 2022 I am getting ready to pull my cooling system stand pipe of to get the new hydraulic wax valve nut welded on and to change a lower pipe and other elbows. I was thinking of changing the thermostat while i have it opened up but i have looked all over for the correct one and i am having a hard time finding the correct part number for my 400 ISL. I find 3 different part numbers at Cummins 3968559,3940632,5284903 not sure what is correct. I have 67000 miles on the engine and no problems with engine running hot but i havent been in the mountains yet and just drove it home 500 miles from Florida. Of course the fan was running wide open the entire time. So do you think i need to change it? If anyone has changed theirs on a 400 isl and knows the part number i would love the info. Thanks, Mike Link to comment Share on other sites More sharing options...
Jdw12345 Posted January 17, 2022 Share Posted January 17, 2022 Just call Cummins and ask for the correct part number, you’ll need the engine number to get the correct part number. 1 Link to comment Share on other sites More sharing options...
wamcneil Posted January 18, 2022 Share Posted January 18, 2022 Parts.Cummins.com. For my 2003 isl 400’s serial number, Cummins says: 3940632 is the original P/N and has been superseded 5284903 is the new P/N Cheers Walter Link to comment Share on other sites More sharing options...
Georgia Mike Posted January 18, 2022 Author Share Posted January 18, 2022 Thanks for the replies. Cummins parts didn't recognize my engine number for some reason and kept giving me a "not found" error. I cleared my browsing data and now it works. Part #3940632 which is now 5284903 is the correct one. Link to comment Share on other sites More sharing options...
Chuck B 2004 Windsor Posted January 18, 2022 Share Posted January 18, 2022 When dealing with a Cummins dealer, make sure that dealer is a Cummins Authorized Distributorship Dealer Link to comment Share on other sites More sharing options...
Dalton07 Posted February 9, 2022 Share Posted February 9, 2022 (edited) I purchased an RV thermostat from Dometic when the factory one in my RV started going out. It replaced my old one perfectly and has been functioning very well for a month now. I love that this thermostat connects to both the air conditioner and the furnace. As you probably know, some models only link to the furnace, which isn’t ideal for someone like me who values convenience. Edited February 13, 2022 by Dalton07 Link to comment Share on other sites More sharing options...
granvillebarker Posted February 19, 2022 Share Posted February 19, 2022 On 2/9/2022 at 2:22 AM, Dalton07 said: I purchased an RV thermostat from Dometic when the factory one in my RV started going out. It replaced my old one perfectly and has been functioning very well for a month now. I love that this thermostat connects to both the air conditioner and the furnace. As you probably know, some models only link to the furnace, which isn’t ideal for someone like me who values convenience. This thread is about the engine thermostat, not the HVAC type. Link to comment Share on other sites More sharing options...
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