Catalytic Converter - California

This procedure covers the removal and replacement of the California-spec catalytic converter on a 2007 Ram 3500 with the 5.9L Cummins diesel engine and 4WD.

Warnings

Tools required

Parts

• California emissions catalytic converter assembly × 1 — Use OEM specification for California emissions compliance
• Exhaust flange gasket × 1 — Use OEM specification
• Exhaust flange nuts × 4 — M10 x 1.5 stainless steel
• Band clamp (if original is damaged) × 1 — 4-inch stainless steel V-band clamp
• Exhaust hanger isolators (if deteriorated) × 2 — Use OEM specification

Preparation

1. Park vehicle on level, solid surface and engage parking brake
2. Place wheel chocks behind rear wheels
3. Allow exhaust system to cool completely (minimum 2 hours after last operation)
4. Spray all exhaust fasteners with penetrating oil and allow to soak for at least 15 minutes
5. Raise vehicle using floor jack at manufacturer's specified lift points
6. Support vehicle securely on jack stands at front and rear frame rails, ensuring adequate clearance to work underneath
7. Remove jack and verify vehicle stability before working underneath

Procedure

1. 1

   Locate and inspect catalytic converter
   The California-spec catalytic converter is located in the exhaust system downstream of the turbocharger. It is mounted with a flanged connection at the inlet (turbo side) and a band clamp or flanged connection at the outlet (towards muffler). Inspect the converter and surrounding exhaust components for damage, identify all mounting points, and verify you have the correct replacement part.
2. 2

   Disconnect downstream exhaust connection
   Locate the connection point between the catalytic converter outlet and the exhaust pipe leading to the muffler. If equipped with a band clamp, loosen the band clamp bolt using a 15mm wrench and slide the clamp back away from the joint. If equipped with a flanged connection, remove the flange nuts using a 19mm socket. Carefully separate the joint - you may need to twist and pull to break the seal.
   ⚠If fasteners are severely corroded and will not loosen, they may need to be cut with a reciprocating saw. Take care not to damage the downstream exhaust pipe if it will be reused.
3. 3

   Remove upstream flange connection
   Locate the flanged connection between the turbocharger outlet and the catalytic converter inlet. Remove the four flange nuts using a 19mm socket. Keep track of any washers or spacers. If nuts are seized, apply additional penetrating oil and attempt removal again after 10 minutes. Support the catalytic converter weight as you remove the final nuts to prevent stress on the turbo mounting.
   ⚠The turbocharger outlet flange can be damaged if excessive force is used. If hardware is frozen, cut the studs rather than risk damaging the turbocharger.
4. 4

   Disconnect exhaust hangers
   The catalytic converter assembly is supported by rubber exhaust hangers. Identify the hanger locations (typically 1-2 hangers along the converter body). Using a pry bar or exhaust hanger tool, carefully lever the exhaust hanger rods out of the rubber isolators. Work methodically to avoid tearing the rubber. If isolators are severely deteriorated, plan to replace them.
5. 5

   Remove catalytic converter assembly
   With all connections and hangers disconnected, carefully lower and maneuver the catalytic converter assembly out from under the vehicle. The converter is heavy and awkward - use caution to avoid injury or damage to surrounding components. Note the orientation and any alignment features for installation of the new unit.
6. 6

   Clean mating surfaces
   Use a wire brush to thoroughly clean the turbocharger outlet flange and the downstream exhaust pipe connection surfaces. Remove all traces of old gasket material, carbon buildup, and corrosion. Clean the flange studs protruding from the turbocharger with a wire brush and inspect for damage. Replace any damaged studs before proceeding.
7. 7

   Inspect and prepare new catalytic converter
   Unpack the new California-spec catalytic converter and verify it matches the original unit in size, inlet/outlet diameter, and mounting configuration. Verify the CARB certification label is present. Check that all flange surfaces are clean and free of debris. Install the new exhaust flange gasket on the turbocharger flange, ensuring proper orientation.
   ℹ️California requires CARB Executive Order (E.O.) certification for all replacement catalytic converters. Verify the new converter has the appropriate E.O. number for this vehicle application.
8. 8

   Position new catalytic converter
   Carefully lift and position the new catalytic converter into place under the vehicle. Align the inlet flange with the turbocharger outlet flange and gasket. Thread the four new flange nuts onto the studs by hand, starting all four nuts before tightening any. Ensure the converter is properly aligned with the downstream exhaust pipe and exhaust hangers are positioned to engage their isolators.
9. 9

   Tighten upstream flange connection
   Using a 19mm socket and torque wrench, tighten the four flange nuts connecting the catalytic converter to the turbocharger outlet. Tighten in a criss-cross pattern in three stages: first to 15 ft-lbs, then to 25 ft-lbs, and finally to 35 ft-lbs. This ensures even clamping force and proper gasket seating.
10. 10

    Connect exhaust hangers
    Install the exhaust hanger rods into their rubber isolators. You may need to use a pry bar to leverage the hangers into position. Ensure the hangers are fully seated and the exhaust system is properly supported without binding or excessive tension. If rubber isolators were damaged during removal, install new ones now.
11. 11

    Connect downstream exhaust connection
    Align the catalytic converter outlet with the downstream exhaust pipe. If using a band clamp, slide the clamp over the joint and position it properly centered. Tighten the band clamp bolt to 45 ft-lbs using a 15mm wrench and torque wrench. If using a flanged connection, install new flange nuts and tighten in a criss-cross pattern to 35 ft-lbs. Ensure the joint is fully seated before final tightening.
12. 12

    Verify exhaust system alignment
    Visually inspect the entire exhaust system from turbocharger to tailpipe. Verify all connections are secure, hangers are properly engaged, and there is adequate clearance between the exhaust system and chassis components, fuel tank, and drivetrain. The system should hang evenly without apparent stress or binding. Make any necessary adjustments before lowering the vehicle.

Reassembly

1. Double-check all fastener torque values before lowering vehicle
2. Verify all exhaust hangers are properly seated and supporting the system
3. Ensure no tools or parts have been left under the vehicle
4. Carefully raise vehicle slightly and remove jack stands
5. Lower vehicle completely to the ground

Verification

• Start the engine and allow it to idle - listen carefully for any exhaust leaks at the catalytic converter connections (a hissing or ticking sound indicates a leak)
• Inspect all connections while the engine is running for visible exhaust gas escaping
• With engine at operating temperature, perform a brief test drive and listen for any unusual exhaust noises or rattles
• After test drive, re-inspect all connections for signs of leaks (black soot deposits indicate a leak)
• Verify engine performance is normal with no check engine lights or loss of power
• If possible, perform a visual inspection of the exhaust system after 50-100 miles of driving to verify all fasteners remain tight and no leaks have developed

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