2004.5-2007 Dodge 5.9L Cummins Intake Horns

Intake air horns on the 2004.5-2007 Ram 5.9L Cummins

The air horn is the cast aluminum elbow that connects the intercooler pipe to the intake plenum cast into the cylinder head. Charge air comes up from the air-to-air intercooler, makes a 90-degree turn through the horn, passes the grid heater and enters the plenum. The factory horn is held by four 10 mm bolts, the dipstick-tube bolt and a band clamp, and it seals to the grid heater with a gasket. Aftermarket horns are built to smooth that 90-degree turn into the plenum.

What fails and why

On this engine the trouble shows up at the joints around the horn. Every time the horn comes off for injector or grid heater work, the gasket can tear, and a torn gasket leaks unmetered, unfiltered air at the horn-to-head joint. Upstream, the factory rubber intercooler boots crack with age, and faster with added fuel or boost. A leaking boot shows up as lost power, a whistle or hiss under boost, higher EGTs and black smoke. Silicone boots with spring-loaded clamps are the replacement.

Stock replacement vs. upgrade

If you are only servicing the truck, the factory horn goes back on with a new heat-resistant gasket, Cummins 3969988, which replaced the pink 3938158. An aftermarket horn makes the most sense when you are already in there or building the charge-air side as a system. Expect modest gains at stock boost: the ECM and wastegate cap boost at about 30-31 psi on 2004.5 and later trucks, so a smoother path mostly helps response. Kits that pair a high-flow horn with new intercooler piping or an upgraded intercooler address more of the path at once, and an upgraded intercooler can lower EGTs, with Diesel Hub citing up to about 200 F. If you add fuel, use CARB EO-numbered products only and verify per product and model year.

What we carry

Wehrli Custom Fabrication (WCFab) offers the 3.5-inch high-flow intake horn and intercooler pipe kit, Stage 1 and Stage 2 high-flow intake bundle kits, and a 3.5-inch silicone boot and clamp kit. Banks Power has the Monster-Ram intake system plus intercooler upgrades in separate 2003-2005 and 2006-2007 versions. S&B makes the 76-1004 performance intake elbow for 2003-2007 5.9L trucks, and MAHLE supplies the G32749 intake heater grid gasket and the MS19355 intake manifold gasket set. For complete intake systems from the filter forward, see intakes; for everything else on this engine, start at the Cummins hub.

Fitment notes

The horns, elbows and horn kits here are listed for 2003-2007, but the intercooler side splits by year. Banks sells one intercooler upgrade for 2003-2005 and another for 2006-2007, and 2005 trucks are commonly reported to have plastic intercooler end tanks while 2006-2007 trucks have metal, so order the version that matches your build. Boot kits are sold by inside diameter, so match the size to your pipe. A 2004.5 truck is titled as a 2004. If you have a 2007, confirm it is the 5.9L and not the 6.7L used on trucks built after January 1, 2007. Verify by VIN when in doubt.

Frequently asked questions

Will an aftermarket air horn add power on a stock 2004.5-2007 5.9L?

Expect modest gains. The aftermarket horn smooths the 90-degree turn into the plenum, but the ECM caps boost around 30-31 psi on these trucks. Treat it as part of a larger charge-air upgrade rather than a stand-alone power part.

What do I need to pull the air horn?

The horn comes off with four 10 mm bolts, the dipstick-tube bolt and a band clamp. Have a new gasket ready before you start, because the old one tears easily. Cummins 3969988 is the heat-resistant gasket to use.

Why is my truck leaking air at the horn after injector work?

A common cause is a torn horn gasket. It tears easily when the horn is removed for injector or grid heater service, and the result is an unmetered, unfiltered air leak at the horn-to-head joint. Replace it with the heat-resistant 3969988 instead of reusing the old one.

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.