2004.5-2007 Dodge 5.9L Cummins Engine Parts

The engine in the 2004.5-2007 RAM 5.9L Cummins

Mid-2004 brought the last and strongest version of the common-rail 5.9L: 325 hp, with 600 lb-ft of torque on 2004.5 trucks and 610 lb-ft from 2005 through 2007. It is a cast-iron inline-six with a cast-iron 24-valve head, a solid-lifter camshaft, a 4.02 in bore, a 4.72 in stroke, 17.2:1 compression and a 1-5-3-6-2-4 firing order. Dressed, it weighs about 1,150 lb.

Cummins stiffened the common-rail block for higher cylinder pressure, with sculpted side walls, stiffening rails and a plate across the oil-pan rail. The front gear case is located by dowel tubes in its lower bolts, so the killer dowel pin worry from 1989-2002 engines does not apply. The 1999-2001 53-block cracking problem is not a 2003-2007 concern either. At stock power, the long block is not the weak link.

What fails and why

Start at the front of the engine. The factory harmonic damper is a cast hub bolted to the crank, a tuned rubber ring, and an outer inertia ring with the serpentine pulley machined into it. Heat, age and flexing break that rubber down. The ring walks out of alignment, rubber squeezes out past the ring face, and the belt stops tracking true. Replace the damper if the index line is more than 1/16 in out; the owner's manual calls for an inspection at 30,000, 60,000 and 90,000 miles. Some owners who kept running a failed damper have reported broken damper bolts and cracked hubs.

The exhaust manifold is a long cast piece on a long engine, and repeated heat cycles crack it, most often on trucks that tow. You will hear a tick or knock that gets louder with rpm, smell exhaust, and find soot streaks at the manifold. Injectors are the other big one. A failed injector driven on can wash a cylinder or dilute the oil: look for white smoke, a dead miss and an oil level that climbs between changes. On trucks with added fuel and the stock turbo, repeated high exhaust gas temperatures can drop a valve seat, which shows up as a sudden miss or knock. The guidance for 2004.5-up engines is a 1,500 F maximum EGT.

Stock replacement vs. upgrade

For a stock truck, OEM-grade parts are the right call. Genuine Cummins gaskets and seals, OEM-grade replacements from Mahle and Dorman, and remanufactured components put the engine back the way it left the factory. Upgrades make sense where added power puts the stress. Head studs and an upgraded head gasket are inexpensive insurance once boost goes above about 40 psi, and running 40-50 psi with fuel to match on factory head bolts is a gamble. For a failed damper on a fueled truck, the recommended replacement is a viscous or elastomer-ring aftermarket damper: it keeps the pulley on the hub so belt alignment cannot drift, and it damps a wider rpm range. Heavy-duty valvetrain parts, billet valve covers and performance oil filters round out the upgrade side.

What we carry

This collection covers the whole engine. Gaskets, seals and head sets come from Mahle and Genuine Cummins, including the Cummins 3937111 front crankshaft seal kit and the Mahle JV1690 rear main seal set. Dayco and Dorman supply serpentine belts, tensioners, idler pulleys, fan clutches and Dorman's 594-356D performance harmonic balancer. D&J Precision Machine builds the heads and crate engines, from a remanufactured cylinder head to Precision Plus and Essential short blocks, long blocks and Ready Run engines. Head stud kits come from ARP and PPE, which also supplies its MicroPure XR oil filter. XDP adds heavy-duty rocker arms, valve springs and bolt kits, and WCFab makes a billet valve cover. Engine oil and additives come from Hot Shot's Secret and Lucas Oil. You will also find parts from Hamilton Cams, Fleece Performance Engineering and Gator Fasteners. For fuel, air and turbo parts, browse the rest of our Cummins parts.

Fitment notes

These trucks were sold as the Dodge Ram 2500 and 3500 in ST, SLT and Laramie trim, as Regular Cab, Quad Cab and, from 2006, Mega Cab. We file them under RAM. The Power Wagon of this era is a 5.7L Hemi truck, not a Cummins. 2007 is a split year: the 5.9L was replaced partway through the model year by the 6.7L, so match parts by engine, not by model year. The valve cover, breather and injector harness changed between 2003-2005 and 2006-2007 engines, so order those by year. The stock damper, Cummins 3903857, is listed for 1994-2006 5.9L engines, and the 6.7L viscous damper is not a direct bolt-on because of fan-pulley clearance. When in doubt, verify by VIN.

Frequently asked questions

Is the 2004.5-2007 5.9L Cummins block strong enough for added power?

The common-rail block was stiffened for higher cylinder pressure, and its gear case is located by dowel tubes, so there is no killer dowel pin to fix. The 53-block cracking issue belongs to 1999-2001 engines. The head clamp is the place to plan ahead: above about 40 psi of boost, head studs and an upgraded head gasket are the recommended move.

How do I tell if my harmonic damper is going bad?

Look at the index line across the hub and the inertia ring. If it is more than 1/16 in out of alignment, or rubber is pushing out past the ring face, replace the damper. Other signs are a visible pulley wobble at idle, more vibration and a belt that will not track straight.

Why is the oil level on my 5.9L going up?

A leaking injector can put diesel into the crankcase, so a rising oil level points at the fuel system, not the oil system. Other signs are white smoke, thin oil and a dead miss. Fix the injector first, then change the oil and filter.

How much oil does the 2004.5-2007 5.9L hold, and how often should I change it?

It takes 12 quarts with the filter. The factory calls for 15W-40 above 0 F or 5W-40 synthetic, changed every 15,000 miles or 12 months in normal service and every 7,500 miles in severe service. For a truck that works hard, the Turbo Diesel Register's injector guide prefers a CI-4+ oil changed at 4,000-4,500 miles.

Do these engine parts fit a 2007 Ram?

Only if the truck has the 5.9L. Trucks built after January 1, 2007 received the 6.7L Cummins, which is a different engine with different parts. Check the VIN before ordering, and call the shop if you are not sure which engine you have.

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.