E. Replace Front Catalyst (MCC), Check/Replace Exhaust Manifold

E. Replace Front Catalyst (MCC) and Inspect/Replace Exhaust Manifold

1. Remove the air injection tube. Disconnect the oxygen sensor connector and remove the heat shield from around the exhaust manifold.





2. Visually inspect the inside of the heat shield for signs of exhaust leakage such as carbon deposits (Figure 12).

NOTE:
If the heat shield shows signs of exhaust leakage, inspect the manifold for cracks. If cracks are found, replace the manifold in step E-12 with a new exhaust manifold, parts package PN C3940376 (Ram 50) or C3940377 (Colt Vista 4WD).

3. Remove the stud nuts attaching the exhaust manifold to the cylinder head.

4. Remove the bolts securing the exhaust manifold to the catalyst case assembly.

5. Slide the manifold and gasket off the studs and remove. Also remove the catalyst case gasket.

6. Raise the vehicle on a hoist.

7. Disconnect the front catalyst (MCC) from the exhaust pipe (Vista 4WD) or underfloor catalyst (UCC - Ram 50).

8. Lower the vehicle.

9. Remove the MCC.

10. Transfer the heat shields from the old MCC to the new MCC.

11. Install the new MCC on the exhaust pipe or UCC.

12. Install the exhaust manifold on the studs. The original gaskets may be reused if the manifold is not replaced.

13. Evenly tighten the exhaust manifold stud nuts to 13 ft-lbs (17 Nm) torque.

14. Evenly tighten the bolts to the catalyst case to 24 ft-lbs (32 Nm) torque.

15. If a new exhaust manifold was installed, transfer the oxygen sensor from the old manifold to the new manifold.

16. Reinstall the heat shield and reconnect the oxygen sensor electrical connector. Reinstall the air injection tube.

17. Raise the vehicle on a hoist.

18. Tighten the nuts connecting the MCC and exhaust pipe or UCC to 25 ft-lbs (34 Nm) torque.

19. Lower the vehicle.