Exhaust Leak on a 400 Cummins

[SPRING_STREET]

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 !!

[CA_Traveler]

A truck diesel shop should be able to do the repair. However, a truck only shop likely would not understand that this is your home or know what's involved working inside the rig. ie Dirty shoes, grease, etc.

So find a shop that understands MHs, including Cummins Coach Care shops.

[H_travels]

What kind of business checks for Class A exhaust leak? Or name of business anyone has used and was satisfied with?

[Ivylog]

More than likely it's a cracked exhaust manifold on the larger of the two parts which is on the driver's side of the MH. You should be able to see black staining and on first firing the engine up you should be able to feel the heat from the leak if you cannot see it. Start soaking the bolts with PB Blaster now and you may be able to slow it down by putting a SS hose clamp over the crack until you can get it fixed.
Glad you found a better place to fix your alternator in two hours labor.

[koda55]

When we had an exhaust leak they found the clamp for the S pipe at the outlet for the turbo was crooked. This allowed the pipe to not seat properly in the turbo. They reseated the exhaust and installed a new clamp. This cureed our noise. We also have the ISL 400 Cummins engine.

[SPRING_STREET]

Executive, I have the Cummins 400 ISL engine. Was at Cummins two weeks ago and had the computer put on it for an alternator issue. The only thing that came up was the alternator and low on anti-freeze which took almost 2 qts. They were told about the exhaust leak but nothing showed up and I had the alternator replaced elsewhere because of a 6 hour difference in labor !

[Executive45]

Black soot is the tell. Surprised your engine check light hasn't come on...maybe it's only a matter of time. You don't say what engine you have but Cummins can hook it up to their computers and tell you in a minute where it is. Meanwhile, check the vacuum line running to your exhaust brake for leaks....Dennis

[Snomas]

Mine showed black soot in the engine compartment.

[Scottiemom]

Ours was fixed this summer as Teacher's Pet mentioned. I first noticed it when we had fumes in the bedroom whenever we would stop for lunch or for the night. So next day before we left, he pulled up the inspection panel in the rear bedroom and I fired the engine. He immediately saw where the leak was. :E

Dale

[hsteinle]

The Cummins 400 ISL has a KNOWN problem of developing a 'leak' in the manifold area around 60,000 miles. It would be best to take it into a Cummins shop and have them check to be sure you do NOT have that developed leak as it CAN cause serious problems including fires.

[wolfe10]

The "look for black soot" IS the correct way to identify an exhaust leak on a diesel.

[SPRING_STREET]

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]

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]

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]

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.