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Call or Text (352) 722-5295Radiators on the 1998.5-2002 RAM 5.9L Cummins
The factory setup is a large crossflow radiator with a coolant recovery bottle, cooled by a viscous fan clutch driven off the serpentine belt. The system holds about 24 quarts. The radiator is one piece of a crowded front stack that also holds the intercooler, the transmission cooler, the A/C condenser and the power-steering cooler, and every piece of that stack needs attention as mileage and power climb. One point that saves misdiagnosis on the 5.9L Cummins: the usual leak in that front stack is the stock intercooler boots, not the cores.
What fails and why
Radiator tanks are an age item on trucks this old, alongside hoses and the fan clutch. A plugged radiator, a tired fan clutch or a low coolant level all end the same way, with the temperature climbing while you tow or pull a grade. That heat is more than an inconvenience here. On 1999-2001 '53' blocks it is one of the triggers for cracks in the thin water jacket below the passenger-side freeze plugs. If coolant is disappearing and the radiator looks dry, inspect that area, and on automatics look behind the transmission heat exchanger.
Stock replacement vs. upgrade
A direct-fit replacement restores the factory design, and that is the right call for a truck doing the work it was built for. The CSF 3273 is sold as an OEM-style replacement, and the XDP XD461 Xtra Cool is a direct-fit replacement. Upgraded radiators are catalogued for 1994-2002 Cummins trucks that work harder or make more power, and the Mishimoto MMRAD-RAM-94 aluminum performance radiator is that option here. If you are adding power or towing more, look at the whole front stack, not just the radiator.
What we carry
Mishimoto offers the MMRAD-RAM-94 aluminum performance radiator and the R1553 replacement radiator, both listed for 1994-2002 Cummins, plus two bundles listed for 1998.5-2002: the MMB-RAM-006 Radiator Essentials Bundle and the MMB-RAM-007 Radiator & Transmission Cooler Ultimate Bundle. XDP's XD461 Xtra Cool direct-fit replacement radiator and the CSF 3273 OEM-style replacement radiator, both listed for 1994-2002 5.9L Cummins, round out the page.
Fitment notes
The standalone radiators are listed for the whole 1994-2002 second generation, while the Mishimoto bundles are listed for 1998.5-2002 only. A 2002 Ram 2500 or 3500 belongs here; 2003 and later HD trucks are a new generation with an all-new frame, so check their fitment separately. If you are looking at the radiator and transmission cooler bundle, confirm on the listing that the cooler suits your transmission, whether that is the 47RE automatic or an NV4500 or NV5600 manual. When in doubt, verify by VIN.
Frequently asked questions
What is the difference between the two Mishimoto bundles?
The MMB-RAM-007 Ultimate Bundle pairs the radiator with a transmission cooler, as its name says. The MMB-RAM-006 Essentials Bundle centers on the radiator. Both are listed for 1998.5-2002 trucks; open each listing to see exactly what is in the box.
Do I need an upgraded radiator on a stock 24-valve?
Not by default. A direct-fit replacement restores the factory design. Upgraded radiators make sense for trucks working harder or making more power, and at that point the intercooler, transmission cooler and condenser deserve the same look.
My truck runs hot when towing. Is it the radiator?
It can be. A plugged radiator, a tired fan clutch and low coolant are the usual suspects, and all three are worth fixing quickly because overheating is a listed trigger for cracking 1999-2001 '53' blocks. If coolant is also disappearing, inspect the passenger side of the block below the freeze plugs.
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.