1989-1993 Dodge 5.9L Cummins Intercoolers & Piping

Intercooler and piping on the 1989-1993 Ram 5.9L Cummins

Dodge added a front-mounted air-to-air intercooler to the 5.9L Cummins partway through 1991. On those trucks, air leaves the Holset H1C compressor, runs through the cooler and rubber boots, and comes back to the cast air horn. Cooler, denser air raises performance potential and efficiency. Earlier trucks send compressed air from the turbo straight to the horn with nothing in between. The advertised rating did not change: every 1989-1993 truck is rated 160 hp and 400 lb-ft. The intercooler's benefit showed up in towing and EGT, not on the spec sheet.

What fails and why

On non-intercooled trucks, heat is the built-in problem. They run higher intake temperatures and higher EGT. The symptoms are high EGT when the truck is working hard and a loss of power once it heat-soaks in summer. On intercooled trucks, the cooler is joined to the turbo and the horn with boots and clamps, and those joints are what hold boost between the compressor and the engine, so they belong on the list when you chase a boost complaint.

Stock replacement vs. upgrade

If your truck has the factory intercooler, keeping its boots and clamps tight is stock maintenance, and upgrading the core is an option documented on built trucks. If your truck is a 1989 to early-1991 without one, adding an intercooler is the change suggested for cooler EGT and better overall performance. Aftermarket intercooling is credited with up to 200°F lower EGT and at least 20 hp. Know what you are signing up for: documented conversions use an adapted core sized for a Ford 7.3L with an install kit, custom brackets and 3-inch piping. It is a fabrication job, not a drop-in.

What we carry

This collection carries the PPE 515303088 3-inch silicone hump coupler. It joins 3-inch charge pipe, the piping size used on documented first-gen intercooler builds, and a documented first-gen build used silicone boots with stainless clamps at its connections. For complete intake systems, browse our intakes category and check first-gen fitment on each listing.

Fitment notes

Match parts to your configuration, not just your year. Non-intercooled and intercooled first-gens use different intake plumbing, and a 1991 can be either one, so look for the cooler at the front of the truck and the boots running to the turbo and horn. Measure the outside diameter of the pipe or outlet you are connecting before you order a coupler, and check the listing for whether clamps are included. If you are converting a non-intercooled truck, coupler sizes follow the piping you build, not the factory setup. Verify by VIN or call us when in doubt.

Frequently asked questions

How do I know if my 1991 Ram came with an intercooler?

Look at the front of the truck and the plumbing around the turbo. Intercooled trucks, built from mid-1991 on, have an air-to-air cooler with boots running from the turbo to the cooler and from the cooler to the air horn. If the turbo pipe goes straight to the horn, your truck is one of the earlier non-intercooled builds.

Can I bolt an intercooler onto a 1989 or 1990 Ram?

Not as a drop-in. Documented conversions use an adapted core, such as one sized for the Ford 7.3L, with an install kit, custom brackets and 3-inch piping. Plan on fabrication time, and plan the coupler and clamp sizes around the piping you build.

Will the PPE 3-inch hump coupler fit my truck?

It fits 3-inch pipe, which matches the piping used on documented first-gen intercooler builds. Factory boot and outlet sizes are not something to guess at, so measure the outside diameter of what you are joining before you order.

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.