A shussssss sound

[kozakvod]

2013 ISX15 2350 recently demandated.

Yesterday while driving down to auction to pick up new load I noticed this shussss sound that stays in the pedal. Let off the pedal sound immediately disappears.

I didn't notice any power loss or MPG loss issue.

Also, a couple of you hear have suggested to get online remotely with Rawze or Uni or Mr. Hag and have them dial in the tune a bit more. While that's a great idea I don't believe that in and of itself is this current issue.

Suggestions?

[tree98]

Air inlet into the compressor sucking air in from a split hose or other break in the line ?? You're not losing boost at all ??

[kozakvod]

(05-10-2020 )tree98 Wrote:  Air inlet into the compressor sucking air in from a split hose or other break in the line ?? You're not losing boost at all ??

If it were a compressor issue it wouldn't matter any about engine rpm would it? Meaning when I'm into the pedal from a stop light changing gears.

As I shift through that noise is there. I do not notice it getting "louder" as RPM increases it seems to be same level, but let off the pedal, sound goes away. Get into the pedal again, sound is back.

Boost pressure loss? Haven't noticed any. I only see the boost PSI drop as the RPM/HP/Torque increase, but it seems to be holding power and boost very well. AND my MPG is good. Well, for a car hauler it's good. Example I mean by that is let's say I'm at 55 mph in 7H at 1600 and I shift to 8L and rpm drops to 1400/1450 or so. I bring the boost up to say 30 psi. As the rpm begins to increase the boost will start to coming back ever so slightly, maybe 5 psi, maybe.

[tree98]

Yeah wouldn't be compressor then. Do you hear it if you rev the engine up while sitting still or only while moving?

[kozakvod]

(05-10-2020 )tree98 Wrote:  Yeah wouldn't be compressor then. Do you hear it if you rev the engine up while sitting still or only while moving?

I only hear it under power. As soon as pedal is backed off sound goes silent.

I am thinking obviously air leak. Maybe on exhaust side because my boost and mpg aren’t being affected. Maybe just my inexperienced diagnosis.

[tree98]

Pressurize the entire engine with 30 psi, you'll find the leak.

[JimT]

If your air intake system doesn't have any significant leaks then I would focus on the exhaust system. One place on the intake side to check is the little rubber/silicon elbow from the air intake to the air compressor. I had one once that was so damaged that it looked like someone scraped it with a cheese grater. Despite the looks and obvious leaking, it didn't significantly affect my boost pressures while driving. However if you pressurize the system to check for leaks it would be easy to find.

A common culprit is the exhaust bellows (the thing that looks like a flex pipe). They develop small cracks over time and will produce a sound like you describe. Sometimes, early on, it will come and go only when you hit bumps, but eventually it will become more consistent. If you haven't recently removed any other exhaust components then this could be your culprit.

If you recently demandated then it could also be one of the other joints leaking a little exhaust. Especially if you didn't put new gaskets on between the exhaust pipes. Being demandated this wouldn't be much of an issue, as long as you don't have a noticeable exhaust leak under the cab, which is a DOT violation.

Hope this helps point you find the problem.

[kozakvod]

I did put all new gaskets on exhaust connections. BUT I also got to thinking that it might be worthwhile to go back under and put a wrench on those ring bands to make sure they’re still tight and that nothing loosened up over my first two trips since demandate.

And Ill check that compressor connector too.

[JimT]

one other thing that just popped in to my mind, not sure if it's valid, but figure i'd mention. it could also be EGR leaking. If you didn't install a blocking plate it could be the EGR valve leaking slightly. Or there could be a slight leak around the blocking plate. These are just speculations, more things to consider.

My first thought when I read your post was the exhaust bellows, so give that a good look.