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Call or Text (352) 722-5295Radiators on the 2004.5-2007 RAM 5.9L Cummins
The 5.9L Cummins uses a crossflow radiator mounted behind the air-to-air intercooler and the A/C condenser, with a large engine-driven fan on a viscous clutch pulling air through all three. It is part of a pressurized system that holds about 7.3 gallons of coolant, and a normal drain-and-fill takes about 6.5 gallons. Because the radiator, intercooler and condenser share one airflow, what happens at the intercooler affects how hard the radiator works under load. It is commonly reported that the intercooler in front of the radiator used plastic end tanks on 2005 trucks and metal on 2006-2007.
What to check before you replace it
When a 5.9L runs hot, check the cheaper suspects first. The viscous fan clutch can lose its silicone fluid, overheat its shear plates or seize. A clutch that lost fluid spins freely by hand and lets the truck run hot towing or in traffic; a seized one roars constantly and is hard to turn. With the engine off, light-to-moderate resistance is normal. Coolant condition matters too: topping off HOAT with green IAT leaves gummy deposits in the system and shortens the life of the fill. If the clutch checks out and the coolant is right, the radiator and the rest of the stack are next.
Stock replacement vs. upgrade
If the truck is stock and the radiator is worn out, an OEM-style replacement brings it back to factory: the CSF 3710 OEM Style Replacement Radiator or the XDP XD296 Xtra Cool direct-fit replacement. If the truck tows heavy or makes more power, the Mishimoto MMRAD-RAM-03 aluminum performance radiator is the step up. Mishimoto also sells bundles for owners replacing more than one cooler at once: the MMB-RAM-001 pairs a radiator with a transmission cooler, and the MMB-RAM-002 heavy-duty bundle adds an intercooler. An upgraded intercooler lowers intake temperatures, worth up to roughly 200 F lower EGT, and reduces the total heat the cooling system has to reject under load.
What we carry
- CSF 3710 OEM style replacement radiator (2003-2009 5.9/6.7L Cummins).
- XDP XD296 Xtra Cool direct-fit replacement radiator (2003-2009 5.9/6.7L Cummins).
- Mishimoto MMRAD-RAM-03 aluminum performance radiator (2003-2009 5.9/6.7L Cummins).
- Mishimoto MMB-RAM-001 radiator and transmission cooler essentials bundle (2003-2009 5.9/6.7L Cummins).
- Mishimoto MMB-RAM-002 radiator, transmission cooler and intercooler heavy-duty bundle (2003-2007 5.9L Cummins).
Fitment notes
Most radiators here are listed for 2003-2009 5.9 and 6.7L Cummins trucks, so they cover the whole 2004.5-2007 run. The exception is the Mishimoto MMB-RAM-002 bundle, listed for 2003-2007 5.9L trucks only. If your 2007 was built after January 1, 2007, it has the 6.7L and that bundle is not for it. Refill with the coolant chemistry already in the truck, which is HOAT to MS-9769 on most 2003-2008 trucks, mixed 50/50 with distilled water. Don't use the 1998.5-2002 green spec on these trucks. When in doubt, verify by VIN.
Frequently asked questions
My truck runs hot towing. Is it the radiator?
Check the fan clutch first. With the engine off, the fan should have light-to-moderate resistance by hand. If it spins freely, the clutch has lost fluid, and that alone makes these trucks run hot towing or in traffic. If the clutch checks out, look at the radiator and the rest of the stack.
Should I buy an OEM-style or an aluminum performance radiator?
For a stock truck that needs a replacement, an OEM-style radiator like the CSF 3710 or the XDP XD296 does the job. If you tow heavy or have added power, the Mishimoto aluminum radiator is the step up. Either way, refill with the right coolant and test the fan clutch.
Why would I buy a bundle with an intercooler?
The intercooler sits in front of the radiator and shares its airflow. An upgraded intercooler lowers intake temperatures, which reduces the total heat rejected to the cooling system under load. The MMB-RAM-002 bundle is listed for 2003-2007 5.9L trucks only.
How much coolant do I need after a radiator swap?
The full system holds about 7.3 gallons, and a normal drain-and-fill takes about 6.5 gallons. Use the same chemistry that was in the truck, mixed 50/50 with distilled water.
Not sure what fits? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.