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Slight over heating under load

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So i got a 3500 dually 5.9 24v common rail with 230k, 48re auto trans. It has a S&B intake and XDP donaldson fuel filter adapter with a programed ECU and carry abou 2k lbs of equipment and tools in the back. When im on idle temp is at 195 but when i go 65mph+ flat or start climbing an incline it generally goes to 220 and up when speed increases. I flushed the coolant and it looks good and clean, oil has no moisture or change in color (T6 rotella SAE 15-w40), threw a new radiator, new thermostat, and new upper radiator pipe. I have a fleece coolant bypass ready to install and fixin to oder a new water pump, but before i start dumping money on my baby, i wanted some of your guys opinion, thoughts, or suggestions. Thank you :)
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· TECH SPECIALIST
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Two things come to mind right away, 195 at idle is way high, temps should drop lower then that. The block mounted heat exchanger will balance the temps from the trans to engine, if the trans temps are high it will drive up CTs.

Check the cooling stack for blockage

Check the bypass valve in the front trans heat exchanger for stuck in bypass mode (not 100% sure on this)

Check the fan clutch
 

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2007 Ram 3500 5.9, mostly stock
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Definitely sounds like the fan clutch may have failed. do you hear the fan kick on high when the temperature rises? Use a large piece of cardboard and push gently against fan while running, the fan should not stop without a decent amount of force being applied. If you do end up needing a new fan clutch make sure you get a Mopar OEM, DO NOT cheap out with something from an auto parts store, it will leave u cooking over beside the road sometime
 

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2007 Ram 3500 5.9, mostly stock
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254 Posts
Ok likely the viscous part is still working if it doesn't stop easily with cardboard. Could possibly be a wiring issue if it's not kicking on high.
I think there is likely another issue because it should not get over 200 when running empty unless it's an extremely hot day driving up a steep hill.
I guess the water pump might be the next thing to check.
 

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2007 Ram 3500 5.9, mostly stock
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254 Posts
Did you use a Cummins t-stat??
 

· Registered
2007 Ram 3500 5.9, mostly stock
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254 Posts
Geno's garage should have it.
 
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