When i tow or run the truck in town or stop and go alot the truck starts to heat up but when i am on the high way towing never dosent it stay cool and if i put the AC on i can see the temp gauge go up a little. i change the coolent and tsat with new it still the same. So Iam thinking its the clutch fan but before i spend more money see what u guys think or if there a way to see if the fan is coming on at all? Ok its a 2003 dually 2wd all stock auto with 280,000. its the frist cummins i own

 

Clean the radiator fins out with low pressure water and check the fins for deterioration.

 

i also tryed this thx any more ideas

 

Fan speed is monitored by the ECM.Check if any DTC is set. Circuit problems will also set a fan clutch DTC's.Do a fan assy spin test.you must do this when the engine is cool.If the fan assy free-wheels without drag(the fan assy will revolve more than five turns when spun by hand),replace the fan drive.

 

I had my 03 overheating when towing. It has 45,000 miles. my cummins had a fan clutch and a fan low speed relay problem that did not trigger any codes in the computer and two five star dealers did not diagnose the problem. I was told to see someone at yet another dealer and this guy knew right off the bat what was going on. They replaced the low speed fan relay and the fan clutch and the problem is gone. the tech told me that I could call a cummins service center and order a 1998 cummins 5.9 thermastat because it's 180* thats 15* cooler than the OE 195* on the 2003 he also told me not to tell any dealer about the thermastat change BECAUSE THEY DO NOT RECOMEND THIS but let me tell you I tow 19,500 LBS over the grape vine in California @ 202* at the top of the grade at 65 mph

 

cool will try that. thx

 

I let it set over night. Then tryed to spin it there tons of drag on it didn t spin at all. what is the DTC iam new at this

 

ok did a little more looking into i found a the way to bring up check engine codes
Turn the key to the on position
Turn the key to the off position
Turn the key to the on position
Turn the key to the off position
Turn the key to the on position
po483 google that and found this P0483 Cooling Fan speed?
thx guys

 

Look at the cooling fan wiring harness that runs between the radiator and the fan shroud. Check and see if the harness is chaffing against the radiator.

MikeyB

 

This engine has a belt-driven cooling fan,not electric motor-driven.So,
I don't think it has a Low speed fan relay.The ECM controls the level of engagement of the fan clutch based on coolant temp,intake manifold temp and A/C status.

 

See in the summer time i would try and put the AC and it would heat up faster?

 

could is be the water pump?

 

A quick way to determine if the pump is working is to check if the heater warms up.A defective water pump will not be able to circulate heated coolant through the heater core.
Since the engine only overheat in stop and go driving, I think the problem is in the viscous fan drive and/or its circiut.As posted above ,did you check the eletrical coonector at the fan shroud for any sign of damage or corrosion?
When it starts to overheat,do you hear clutch engaging?You should be able to hear the fan noise to be louder(roaring).

If everything checks out OK,take it t a shop that has access to a DRB III scan tool to check fan speed and duty cycle.

 

no i have good heat . still have to the loom of and look at the wiring.
thx for the help guys

 

its just a thought, but get yourself a new temperature guage and temporarily install it under the hood. Take it for a drive and when the factory guage gets hot, pull over and check the actual temp on your other guage. Caterpillar has some adhesive tape that permanently changes colors when exposed to increasing heat, can't remember the part # for them but a good parts guy could find it.
Another thing, does the smoke output increase when you think its getting hot?.. Boiling out coolant?.. Is the transmission getting hot causing increased heat load on the cooling system?.. Just some other things to check if you haven't already. One other thing, it is possible that the impeller on the pump has started erroding causing a loss of pump outlet pressure, since this is/was and industrial engine,there should be a test port ot put a pressure guage on it, you will have to call a Cummins dealer to get the specs on what it should be....