Turbo whistle/hiss

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Turbo whistle/hiss

September 30, 2013, 02:13:13 pm

Cummins 400 ISL. Today noticed that when my turbo pressure exceeds 15 psi, I start to hear a whistle/hiss and it continues if the turbo stays above 15 psi. If I lift off the throttle the pressure drops and the sound goes away. Does not matter what speed I'm going. This is a new noise that I've never heard before.

What is it?
What broke?
Can I drive another 300 miles without damaging something?

Re: Turbo whistle/hiss

Reply #1 – September 30, 2013, 02:35:19 pm

Mark,

Check all boots between turbo and engine-- turbo to pipe, pipe to CAC, CAC to pipe and pipe to intake. Hopefully, the problem will be with one of those. If not look at the CAC itself.

If you can generate 15 or more PSI of boost and drive slowly enough that it would not, under normal conditions need much more, it is unlikely that you will do damage in 300 miles. If this is 300 miles of mountain driving, a different matter.

Re: Turbo whistle/hiss

Reply #2 – September 30, 2013, 03:02:11 pm

Thanks Brett. I'll check all the boots as soon as the engine cools down. I'm in Lexington KY and headed for Chicago so all the hilly stuff should mostly be behind me.

Should I get to a Cummins Coach Care shop or will any Cummins facility be able to service this? I don't want to have any other trouble other than what I already have.

Re: Turbo whistle/hiss

Reply #3 – September 30, 2013, 03:19:14 pm

Turbo whine and/or loss of boost can probably be addressed by any diesel shop.

Have you noticed a reduction in maximum boost, or just the whistle when on higher boosts?

Brett

Re: Turbo whistle/hiss

Reply #4 – September 30, 2013, 03:30:00 pm

Yes I did notice a slight reduction of power. The problem is that I've never looked at the boost readout on the "driver info center" before this so I don't know what is normal. Seat of the pants tells me there is less power. The max today was 21 psi through the Cumberland gap on a couple of steeper grades.

Re: Turbo whistle/hiss

Reply #5 – September 30, 2013, 04:40:30 pm

OK - looked at all the boots, clamps, pipes - the whole flow path and did not find anything, not even disturbed dirt/grime. Looked at the CAC input/output connections and that looked like it has always looked.

So what does that leave as a possible cause?

Re: Turbo whistle/hiss

Reply #6 – September 30, 2013, 04:52:11 pm

I would check the CAC for a crack or split seam. If you are loosing power then the failure is surely a crack or split in the seam of the CAC. Loose clamps would not account for that much of a power loss.

Re: Turbo whistle/hiss

Reply #7 – September 30, 2013, 05:06:32 pm

Thanks all. While it is still light I'll wrench check the clamps and then reinspect the CAC.

Re: Turbo whistle/hiss

Reply #8 – September 30, 2013, 05:47:11 pm

Dave - I just tightened/checked all clamps with a wrench and restarted the engine. With the hatch open and the wife pressing on the accelerator and me standing by the engine the hiss sounds a little more like a squeal. So, even though I did not take it for a ride it seems like the noise did not lessen and it seems to be coming from the turbo itself.
Anny - did not find any splits or cracks in the CAC.

Re: Turbo whistle/hiss

Reply #9 – September 30, 2013, 06:04:57 pm

You might want to check hoses really careful . You might have a split in the hose. Ours split as soon as we got our CAC changed. But that was due to our friendly Little Rock Cummins dealer putting the hose clamp on sideways, half on turbo pipe and just on hose so cut into. Here are some pics of where our CAC was leaking and the hose. The hose is at the top of the motor by the turbo under the engine hatch. We used JB Weld until we could get somewhere to get it fixed.
We have used the Cummins dealer in Rock Island, Ill and like them.

Re: Turbo whistle/hiss

Reply #10 – September 30, 2013, 06:20:53 pm

If you think it may be a squeal rather than air leak, open the back hatch and check the belts-- do it with dash A/C turned on and off.

If so, stop the engine and check belt condition. If cracked, replace. If shiny, remove belt (noting its routing) and rotate each item it turns by hand to make sure a bearing is not frozen up. Removal is easy with just a rachet to detension the automatic tensioner. Be sure to check the tensioner bearings as well.

Brett

Brett

Re: Turbo whistle/hiss

Reply #11 – September 30, 2013, 06:30:37 pm

Quote from: Mark Benko – September 30, 2013, 05:47:11 pm

Dave - I just tightened/checked all clamps with a wrench and restarted the engine. With the hatch open and the wife pressing on the accelerator and me standing by the engine the hiss sounds a little more like a squeal. So, even though I did not take it for a ride it seems like the noise did not lessen and it seems to be coming from the turbo itself.
Anny - did not find any splits or cracks in the CAC.

Get a stick and place one end on the turbo and the other end of the stick to your ear. If there is a squeal coming from the turbo, the stick will transmit the sound clearly to your ear. Old truckers trick!

Re: Turbo whistle/hiss

Reply #12 – September 30, 2013, 06:37:16 pm

Will it remove the ear wax too?

Re: Turbo whistle/hiss

Reply #13 – September 30, 2013, 07:05:00 pm

Brett & Anny - thanks for more things to check and tools to do it with! But seeing that the sun is setting I think I'll resume my investigation in the AM before I attempt to check/remove belts or remove any earwax!

Re: Turbo whistle/hiss

Reply #14 – October 02, 2013, 09:01:35 pm

Mark,
Any update or additional info on your turbo issues?
BTW, glad you were at the GV. A lot of grins and giggles even with missing out on our door prize!

Re: Turbo whistle/hiss

Reply #15 – October 05, 2013, 02:43:56 pm

Bill - turns out there is an exhaust manifold leak right next to the turbo and that was what I heard. Cummins will repair. There is another issue which I'll report on in a few days once I get more info.

Re: Turbo whistle/hiss

Reply #16 – October 05, 2013, 03:25:09 pm

Quote from: Mark Benko – October 05, 2013, 02:43:56 pm

Bill - turns out there is an exhaust manifold leak right next to the turbo and that was what I heard. Cummins will repair. There is another issue which I'll report on in a few days once I get more info.

We also had an exhaust manifold leak on a ISL 400 with another coach. A exhaust manifold leak can make the exact same noise as a belt squeal. The manifold is a two piece unit on most Cummins. You will also find that this problem is very common with Cummins and is fixed when they place a heavier gasket when replacing the manifold. Now you can throw away that can of belt dressing since the squeal is not belts!

Re: Turbo whistle/hiss

Reply #17 – October 05, 2013, 03:42:30 pm

Quote from: anny – October 05, 2013, 03:25:09 pm

...Now you can throw away that can of belt dressing since the squeal is not belts!

But it sure would be nice if belt dressing fixed everything!

Re: Turbo whistle/hiss

Reply #18 – November 08, 2013, 02:55:47 pm

Just wanted to update this thread with the final resolution to the whistle/hiss. Cummins installed a new manifold which when I looked at it later, seems to be a bit beefier than the original one. See the pics below.

The other issue discovered was that the CAC did have a split seam. Nice call Anny.

Long story short, replacing the CAC took a few weeks. Foretravel had 3 on order for restocking so I got one of those when they came in. The good news was that as long as the radiator was out I had Cummins send it to a radiator repair shop for a good cleaning inside and out. Got new Shell Rotella ELC as well. Now that all is back together and working great my gas mileage should return to normal and I learned that my max boost is 31 psi. Price for all of this was about 5.5 coach bucks.

Thanks all for the help.

Re: Turbo whistle/hiss

Reply #19 – November 08, 2013, 03:37:17 pm

wow, that is why I fixed my CAC when I found 3 holes in it. The co' that makes them in Corpus Christie sells them for $1400 and FOT quoted me $3300 at the time. My cost of fixing was $64.00 contrary to what everyone told me that it could not be fixed. Over a year later and it is still going strong-tested by me up to 45lbs pressure.
Must be nice to be rich??
John H