1998.5-2002 Dodge 5.9L Cummins Exhaust Manifolds

Exhaust manifolds on the 1998.5-2002 RAM 5.9L Cummins

The 24-valve 5.9L Cummins is an inline-six, and its factory exhaust manifold is a cast-iron six-port casting that runs the length of the head and feeds the wastegated Holset turbo. That long span, heated and cooled every time you drive, is the reason it cracks. Every manifold job on this truck starts with the same question: put back a stock casting, or move to a design built to live with the heat.

What fails and why

Cracking is the documented failure, and it shows up on high-mileage and high-EGT trucks. The symptom is hard to miss: a loud ticking or knocking that gets louder with engine speed, often with an exhaust smell or soot streaks around the ports. A warped manifold also lets go at the manifold-to-head joint and the turbo flange, which adds ticking at idle and a loss of boost. Repair it promptly, because the cracks keep growing. Heat speeds all of this up. Towing and tuned trucks that see sustained pre-turbo temperatures above 1,200-1,250 F put the turbo and pistons at risk, and a pyrometer probe in the manifold is how you watch that number.

Stock replacement vs. upgrade

A stock truck that just needs a manifold can go back to factory spec with a Cummins genuine casting, new gaskets and fresh hardware. If the truck tows, runs tuning or has cracked a manifold before, the fix the aftermarket settled on is a ported manifold: three-piece slip-joint designs from ATS and BD, or one-piece stainless. BD's three-piece manifolds also come in T3 and T4 flange versions for turbo upgrades, so if a bigger turbo is in the plan, choose the flange with that in mind. Either way, plan on new gaskets and hardware with the manifold; the kits below cover both.

What we carry

For a straight replacement there is the Cummins 5254373 genuine manifold for 1998.5-2002 5.9L trucks and the BD Diesel 1045947 manifold. The ATS Pulse Flow exhaust manifold kit covers 1994-2002 5.9L trucks, and ATS also lists a manifold-to-head gasket and a 45 mm wastegate adapter. Gaskets come from MAHLE, with the MS19225 set, and from BD in several versions. Hardware is the deepest part of this group: stud kits from Gator Fasteners in black oxide or chrome, from Fleece Performance Engineering with 7 mm external hex or 4 mm Allen socket heads, and from Mishimoto and PPE, plus bolt-and-spacer kits from PPE and BD and a stainless bolt kit from XDP. The main exhaust section has the rest of the system.

Fitment notes

The genuine Cummins and BD manifolds here are listed for 1998.5-2002 only, the 24-valve years in the Dodge Ram 2500 and 3500. The ATS kit lists 1994-2002, so it spans the 12-valve years too. Most of the hardware and gaskets carry wider ranges, some starting in 1989 or 1994 and running into the 6.7L years, so read the range on each listing. Stud kits come with different head styles; pick the one that suits your tools and the clearance around the manifold. If you change turbos, check the manifold's turbo flange first. Verify by VIN, and call if you are unsure.

Frequently asked questions

How do I know my exhaust manifold is cracked?

Listen for a loud ticking or knocking that climbs with engine speed, and look for soot streaks or an exhaust smell around the ports. Ticking at idle with a loss of boost points to a leak at the head or turbo flange after the manifold has warped.

Should I replace a cracked manifold with stock or aftermarket?

A genuine Cummins manifold puts a stock truck back to factory spec. If the truck tows heavy, runs tuning or has cracked one before, a three-piece ported slip-joint manifold from ATS or BD, or a one-piece stainless manifold, is the accepted fix for the cracking.

Do I need new studs when I replace the manifold?

Plan on it. The joints at the head and turbo flange are where leaks start once a manifold warps, and fresh gaskets and hardware are what seal them back up. The stud and bolt kits here from Gator, Fleece, Mishimoto, PPE, BD and XDP all list the 1998.5-2002 years in their ranges.

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.