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99 5.9 overheating while towing

57K views 37 replies 25 participants last post by  Dodge2002skull 
#1 ·
I have a new issue. While towing my 34' fifthwheel up 7% grade, my temp shot up to max. I changed the clutch fan cause it wasn't kicking in like it use to. That helped but still running out of the operating range. Turning down chip didn't help. Drained my radiator down to check if was clogged up but it looks great. Had some stuff in fins but washed them out. Thermostat maybe? Any input would be helpful. Never ran hot before.:CRY:
 
#33 ·
Having the same issue

I am having the same issue with over heating and I have replaced the radiator, thermostat, fan clutch, put on a breather canister, but it is still overheating while towing a 10,000lb trailer up the hills. I am doing about 55 MPH. My transmission temp is about 165 and exhaust gas temps are about 1300 max on the climb. I will check out the transmission cooler idea. Any other thoughts?
 
#35 ·
Also just because you bought a new one doesn't mean it works.. the trend seems to be make money first then make things so they work. I replaced my thermostat but i checked it in a pot of boiling water to see what temp it opened up at. first one was over 10 degrees off to the high side. NOT! went thru 2 clutch fans b4 i went back to dodge one. aftermarket ones usually don't have feature where they lock up 100% at idle even when hot unless they are at lock up temp. They would not lock up untill the truck was almost into the red. The dodge one sounds like a dang airplane when it kicks in. You should hear that. You will not miss it, It's loud if it's working. I'm sure there is a couple aftermarket ones that work good.. i just didn't find any.. they were not cheap either over $120. Dodge one was around $160. Open your cap and let your truck warm up.. you should notice a big difference in the amount of water flowing from cold to hot.
 
#36 ·
If you have a cummins dealer nearby, I'd get the cummins tstat, vs getting the dodge one from the dealer...I think I paid about 45-50 for mine, on my 01, when I replaced it, as the old one had stuck open. For those of you with manual trannys, as long as your radiator isn't gunked up, when pulling those steep grades, just downshift, and let the RPM's run about 2500. That's what I did when I moved from California to Indiana, in the middle of the summer. Temps would start creeping up, especially around Denver, but I just downshifted to 4th, and ran the truck at 2500 RPM. Doing this, I could watch my temp guage drop, as I was still pulling strong uphill.
 
#37 ·
my 99 as well as two friends' 99 trucks had same problem all three were cured by a good cleaning of radiator fins including degreasing due to breather getting oil all over then dirt and bugs etc. clogging it all up . those with worse problems ... good luck and please post how you solve them.
 
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