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Call or Text (352) 722-5295Radiators for the 2003-2004 Ram 5.9L Cummins
The first common-rail Cummins trucks use a cross-flow radiator and an engine fan driven through a fan clutch, cooling a system that holds roughly 7 to 8 gallons of coolant depending on the source. The factory fill is Mopar 5-year/100,000-mile HOAT mixed 50/50 with distilled water. The radiator is one layer of a stack. Packed in with it are the air-to-air intercooler, the A/C condenser, the transmission cooler and the power-steering cooler, all sharing the same airflow. That makes a radiator job a good time to look at the rest of the stack, and it is why some of the parts here are bundles that replace more than one core.
What fails and why
No widespread radiator failure pattern turned up in our research for these years. What does happen is gradual. Aging coolers lose capacity, and as the stack clogs with debris, transmission and intercooler temps climb when you tow. High temperatures are the single most damaging factor for powertrain life on a working truck. On automatic trucks, the 48RE starts protective downshifts once fluid temps pass 260 degrees F while towing. Overheating itself is listed as a crack contributor on 24-valve Cummins blocks, and coolant loss and temps that climb on grades are the warning signs. A radiator that cannot keep up is worth replacing before it causes a bigger repair.
Stock replacement vs. upgrade
An OE-style replacement radiator restores factory cooling and is the right answer for a stock truck with a tired core. CSF, Mishimoto and XDP all offer direct replacements for these years. An aluminum performance radiator is the upgrade for trucks that tow heavy or work harder than stock, and the Mishimoto MMRAD-RAM-03 fills that role. If the transmission cooler and intercooler are as old as the radiator, a Mishimoto bundle replaces them in the same job. Heat on the transmission and charge-air side is a real concern on a towing truck, so a bundle covers more than coolant temperature.
What we carry
- CSF 3710 OEM-style replacement radiator, listed for 2003-2009 5.9L and 6.7L trucks.
- XDP XD296 Xtra Cool direct-fit replacement radiator, listed for 2003-2009 5.9L and 6.7L trucks.
- Mishimoto R2711-MT replacement radiator and MMRAD-RAM-03 aluminum performance radiator, both listed for 2003-2009.
- Mishimoto MMB-RAM-001 radiator and transmission cooler essentials bundle, listed for 2003-2009.
- Mishimoto MMB-RAM-002 radiator, transmission cooler and intercooler heavy-duty bundle, listed for 2003-2007 5.9L trucks only.
Fitment notes
Per Mishimoto, radiators for these trucks fit 2003-2009 5.9L and 6.7L Ram 2500 and 3500, which is why most listings here carry that range. Intercooler parts are different: Mishimoto's intercooler pipe and boot kits fit 2003-2007 only, and the MMB-RAM-002 bundle with its intercooler is listed for 2003-2007 5.9L trucks. Nothing here fits a Ram 1500; these trucks were sold as Dodge Ram 2500 and 3500. Refill with coolant that matches what is in the truck. Confirm any radiator with the fitment checker on the product page, or call with your VIN.
Frequently asked questions
Should I replace just the radiator or the whole cooling stack?
It depends on age and use. If the transmission cooler and intercooler are original on a high-mileage tow rig, a Mishimoto bundle replaces them alongside the radiator in one job. If only the radiator is the problem, a single CSF, XDP or Mishimoto replacement does the job.
Is an aluminum performance radiator worth it on a 2003-2004 Cummins?
For a truck that tows heavy, an aluminum radiator and a complete silicone hose kit are the documented starting point for cooling upgrades on these trucks. For a stock truck that works light, an OE-style replacement restores factory cooling and is the simpler choice.
Will a radiator listed for the 6.7L fit my 5.9L?
The radiators in this collection are listed for 2003-2009 5.9L and 6.7L trucks, so the same radiator covers both engines. Intercooler parts do not cross over the same way; they fit 2003-2007 only. Check each listing's year range before you buy.
Not sure what fits your 2003-2004 Ram? Call the shop at the number in the header, or use the fitment checker on any product page. We install everything we sell.