Forum Discussion

SPRING_STREET's avatar
SPRING_STREET
Explorer
Sep 11, 2014

Exhaust Leak on a 400 Cummins

Can anyone tell me how to check for an exhaust leak on a diesel?? Have been hearing what sounds like an exhaust leak when driving with the window down on the highway. More noticeable when you have the barrier separating the lanes, and also when I use the engine brake. Had someone rev the engine when the RV was parked but couldn't find anything, so I assume it needs to be under a load. Also guess it may be in the Turbo if that's possible. Any comments appreciated !!
Class A
  • SPRING_STREET's avatar
    SPRING_STREET
    Explorer
    Sep 11, 2014
    OP here, Also wanted to mention that my exhaust comes out the right side and the noise sounds like it's on the left side and I do have the side radiator on left side
  • Teacher_s_Pet's avatar
    Teacher_s_Pet
    Explorer
    Sep 11, 2014
    Ours is a Cat 350...had a leak fixed this summer. Elbow from exhaust brake to muffler, 1/2" hole under heat shroud, new pipe + labor $340.
  • rav's avatar
    rav
    Explorer
    Sep 11, 2014
    we had one on ours, same as you, heard it driving with the window open- I felt around the exhaust pipe (cold) and finally found the leak under the heat shield sleeve.
  • ScottG's avatar
    ScottG
    Nomad
    Sep 11, 2014
    Look for black soot marks emanating form the manifold and onto the side of the head. Most likely in the rear third of the manifold. Also look for cracks on the "ears" that the mounting bolts go through.

About Motorhome Group

38,706 PostsLatest Activity: Feb 01, 2025