Forum Discussion

hertfordnc's avatar
hertfordnc
Explorer
Jul 16, 2014

dodge 3500 cummins clutch fan engages on flat with no load

I've had this 2003 for just a month, still figuring things out.

With the AC on, running empty on flat ground at 60mph the temp rises to about 210 and the clutch fan engages until the temp drops.

Outside temp is 85f or so.

Is this normal?

I'm thinking the truck is struggling to stay cool with no load and it's not ready to pull a trailer up and down hills.

Or is the hot AC CONDENSOR creating more heat than the airflow can disperse?

Thanks

87 Replies

  • rhagfo wrote:
    You should never be above 190 without a load! Replace the T-stat as mentioned before with a Cummins T-stat. Make sure the outside of the radiator is clean and oil free, check the water pump, simple two bolt replacement.
    I only got my 01 up to 205 pulling a 7% grade on a 95 degree day running at 19,000# GCVW.

    I have to politely disagree with the 190 temp. Mine will run between 190 to just above 200 (according to the dash gauge) unloaded based on outside temperature.

    To the OP, your fan will kick on and off periodically when running your AC on max(or recycle whichever term you prefer). This is in the computer by design. There is an electronic link to it. Many people have even tapped into it and put a manual switch so they can force the fan on whenever they want.

    If your truck is not overheating you are ok. You need to worry if you have the AC on and never hear the fan come on.
  • My 04 does that, on 80* or higher temps. Dealer says it's normal and mine had the thermostat and anti-freeze changed.
    If you don't know if the cooling system has had the 100,000 or five year service I would have it done. Also I would change the belt and all of the hoses at the same time.

    Don
  • wcjeep wrote:
    Are you sure the clutch fan is engaging? The mechanical clutch fan sounds like the truck is preparing for take off when it engages. If the temp is rising to 210 then drops without the jet engine roar it sounds like a slow to react thermostat.


    My fan is super quiet, even when engaged and properly operating (checked with a DRBIII). My dads 06 fan is much louder, so I am not sure what the difference is from 05 to 06.

    rhagfo wrote:
    You should never be above 190 without a load! Replace the T-stat as mentioned before with a Cummins T-stat. Make sure the outside of the radiator is clean and oil free, check the water pump, simple two bolt replacement.
    I only got my 01 up to 205 pulling a 7% grade on a 95 degree day running at 19,000# GCVW.


    I was hitting 213° last week at 19K GCW in temps from 86°-102°.
    That's pretty cool for that much weight! The thermostat isn't even full open, unless you swapped a 180° in. The 2nd gens generally run a little lower EGTs and power, so that will effect coolant temp too.
  • rhagfo's avatar
    rhagfo
    Explorer III
    You should never be above 190 without a load! Replace the T-stat as mentioned before with a Cummins T-stat. Make sure the outside of the radiator is clean and oil free, check the water pump, simple two bolt replacement.
    I only got my 01 up to 205 pulling a 7% grade on a 95 degree day running at 19,000# GCVW.
  • Are you sure the clutch fan is engaging? The mechanical clutch fan sounds like the truck is preparing for take off when it engages. If the temp is rising to 210 then drops without the jet engine roar it sounds like a slow to react thermostat.
  • I would put a new thermostat in it. The cooling system is so large on these trucks that the thermostat rarely goes full open, so they develop wear spots that take more heat to crack it open. What you are describing can occur on an old thermostat.

    Go genuine Cummins, from Cummins and NOT Dodge.

    For reference the 190° thermostat is what your truck uses. It cracks at 190° and goes full open at 207°, max allowed is 225°. If your pulling a big load up a big hill on a hot day 215° isn't a big deal. I find it hard to break 215°, but getting there occurs a few times a year when towing.
  • I would say it has a problem. Could be a thermostat or a water pump problem if the radiator looks OK. At any rate should be an easy fix.