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Call or Text (352) 722-5295Air intake on the 2003-2004 Ram 5.9L Cummins
The third-gen heavy-duty Ram put the airbox at the radiator support. On 2003-2004 trucks it is a sealed box fed only from the passenger fender, with a fender liner that keeps under-hood heat away from an inlet of about 19 square inches. From the box, a 4 in tube carries air to the Holset turbo. Boosted air then runs through the air-to-air intercooler and into the cast-aluminum intake horn on the head of the 5.9L Cummins. The grid heater is sandwiched between the horn and the intake manifold. It is the only cold-start aid on this engine; there are no glow plugs.
What fails and why
The intercooler boots are the part that actually breaks. The stock boots are well known for cracking, and even a small leak brings a noticeable drop in power and a rise in exhaust gas temperature. When one blows off you will know it: a sudden loss of boost, a whoosh under load, black smoke and high EGT. Age and heat cycles cause it, and tuned trucks get there sooner.
The rest of the system is about restriction, not breakage. TDR's testing found the paper filter is the biggest restriction on a 2003-2004 truck and the small box inlet is the second. The factory intake horn is the other bottleneck: its angular shape creates turbulence and its smaller diameter chokes flow. That is a design limit rather than a wear item, and it shows up as higher EGT and slower spool once fueling has been added.
Stock replacement vs. upgrade
Be realistic about a stock truck. Diesel Power magazine ran six aftermarket intakes against the stock system on a stock 2005 truck and none of them beat it. TDR reached the same conclusion: airflow is set by displacement, rpm, volumetric efficiency and boost, not by the filter. A more restrictive filter even gave quicker boost response and more low-end torque, giving up only 2 to 3 hp above 2,700 rpm. If your truck is stock and works for a living, a good replacement filter and fresh boots are the right place to start.
Once you add fuel, the order matters. TDR's sequence is the filter first, then the box inlet, then the tube. On a 2004 High Output 3500 dually, opening the sealed box inlet by 12 square inches and ducting cool air to it improved boost response and power above 2,700 rpm. Next comes a larger-plenum horn with smooth radius turns, which cuts pressure loss and is usually installed along with turbo or fuel work. Silicone boots with spring-loaded or T-bolt clamps stop blow-offs. For a street truck, buy an intake that carries a CARB EO number; Banks and S&B are among the brands that offer EO-numbered intake kits.
What we carry
On the filter and intake side, we stock S&B (the 75-5094 cold air intake, KF-series replacement filters, the WF-1017 filter wrap and a cleaning and oil kit), Banks Power (the RAM-Air cold air intake, the Monster-Ram intake system and the 42148 filter element), MAHLE (the LX2947 air filter, an intake manifold gasket set and head sets) and Wehrli Custom Fabrication (Stage 1 and Stage 2 high-flow intake bundles, a 4 in intake kit, intercooler pipes and silicone boot and clamp kits). For the charge-air side there are Mishimoto intercoolers, pipe kits and factory-fit boot kits, CSF OEM+ replacement and heavy-duty intercoolers, a BD Diesel intercooler replacement pipe and a PPE silicone hump coupler. Electrical and sealing parts round it out: a genuine Cummins MAP sensor and heater grid, XDP air temperature and throttle position sensors with heavy-duty grid heater wiring, the Alliant Power grid heater gasket set, and BD Diesel Positive Air Shutdown valves. Shopping for more than one truck? See all intakes.
Fitment notes
The 2004.5 update changed the airbox. The inlet grew to about 26 square inches, a vertical baffle was added to pick up cold air at the wheel-well lip, and the fender liner was dropped. Because the airbox, intake tube and fender liner differ, intake kits are split between 2003-2004 and 2004.5-2007. Some parts here, like the S&B 75-5094, cover 2003-2007 in one part number; others list a narrower range, so read the years in the title. These trucks were sold as the Dodge Ram 2500 and 3500, and nothing on this page fits a Ram 1500. If you are adding an aftermarket horn, make sure it leaves room to pull the air tube, which has to come off for injector or valve-cover work. When in doubt, verify by VIN.
Frequently asked questions
Will a cold air intake add power to my stock 2003-2004 Cummins?
Not much. Testing by Diesel Power magazine and TDR found the factory system flows about as well as aftermarket kits on a stock engine, because airflow is set by displacement, rpm and boost rather than the filter. Intakes start to pay off once fueling has been added.
Why does my truck suddenly lose boost and blow black smoke under load?
Check the intercooler boots first. The stock boots crack and blow off, and a leak shows up as a sudden boost drop, a whooshing sound, black smoke and high EGT. Silicone boots with spring-loaded or T-bolt clamps are the fix.
Is a cotton gauze filter better than paper for towing?
Cotton gauze flows the most, but TDR noted a slight loss of filtration efficiency and dirt-holding capacity. For towing or dusty roads, a stock-style or dry element is the better choice. Filter quality matters on this engine: a torn-down 2003-2004 turbo showed compressor blade wear from poor filtration.
Do 2004.5-2007 intake parts fit an early 2004 truck?
Not always. The 2004.5 trucks got a larger airbox inlet, a cold-air baffle and no fender liner, so many intake kits are split at 2004.5. Make sure the product title covers 2003-2004 before you order, and verify by VIN if you are not sure which half of 2004 your truck came from.
Where should I start if I want more airflow?
Start with the air filter. TDR ranked the paper filter as the biggest restriction, then the box inlet, then the tube. If your intercooler boots are still original rubber, replace them with silicone at the same time so a blown boot does not undo the work.
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.