John Deere 425 thermostat question

Dromunds · Jun 9, 2020

Suddenly, the temp gauge on my JD 425 is running real hot and I suspect the thermostat. I looked online and I saw that John Deere went from a 160 degree stat to a 180 degree to comply with some EPA regulation apparently. Some guys say the 180 degree stat makes their tractor run poorly and some guys say they were told by Deere to change to a different carb to ameliorate the poor running issue. I called our local JD dealership and the old part number (AM109396) is now replaced by part number M123434 which indeed is 180 degree. He's never heard of anyone having to switch carbs after putting in the new stat. Does anyone have any information about this? Also, does anyone know if NAPA or any other aftermarket stat will replace the JD? I've heard Auto Zone part number 7203-160 will work but others report the AZ part does not have a taper and nobody that I saw actually said they used it successfully. Thanks for your help.

Wisconsin Cowman · Jun 9, 2020

I have never replaced a carburetor on a 425 when changing the thermostat. I put in the new thermostat M123434 and that’s it. Make sure the radiator is clean. May want to verify engine temperature with a laser thermometer. Not that you have bad gauge cluster. Better off using the Deere part probably not going to save yourself any money buying from an auto parts store. Your Deere dealer probably has one on hand.

Dromunds · Jun 9, 2020

Thanks for the reply. I checked and a nearby dealer has one in stock so I guess I'll put 'er in and see how she runs.

John Deere 425 thermostat question

Dromunds

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Wisconsin Cowman

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Dromunds

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