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Old 10-21-2021, 09:31 PM   #1
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Location: Waldorf, MD
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Soot on rear of Coach

I have a concern regarding soot on the rear of my coach and on the front of the toad.

After a run from Needles to Albuquerque and then to Amarillo I noticed a black soot on the rear of the coach and front of the toad. It's not oily just a dry soot. You can wipe some off without leaving a mark and the film on your finger is dry.

There are no fault codes, all the gages are normal, and the coach runs just fine. No noticeable change in performance - up, down, and on flat ground. Oil level is at the full mark and no leaks or drips from the engine or trans.

Talked to two different Cummins Service Centers and got the same recommendations from each. One also looked at the toad and was able to run his finger through the soot on the toad. Both said to keep on driving, keep checking the oil level and go on home to Maryland. Take it to a local Cummings Service Center and have them check things over to see if there is anything wrong. Without fault codes there is nothing they can do.

If anyone else has had this happen I would be glad to hear what caused their problem and what was done to fix it if it needed fixed.

So tomorrow I am leaving Amarillo tomorrow and working my way back East to Gaffney. Maybe during the annual maintenance they will find something to clear things up.

Thanks - David C.
2018 Dutch Star 4018, 2013 Chevy Equinox LTZ, Retired USAF 92, Retired FG 2012. Don't grow up it's a trick.
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Old 10-21-2021, 09:53 PM   #2
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Black soot from the exhaust , can be a result of not enough air for complete combustion , did the mechanic check the air filter ?

Not just the filter minder ; those often lie ; need to look inside the filter housing.
99DSDP 3884, Freightliner, XC, CAT 3126B, 300 HP /ALLISON 3060
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Old 10-22-2021, 09:56 AM   #3
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Could possibly be from a regen cycle in the emissions system. Could you turn the exhaust tip to the right?
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Old 10-22-2021, 11:20 AM   #4
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I thought of exhaust soot as well, not oil. Soot from a regen is a good suggestion, but in your year coach, it should not be happening on any regular basis. You have a DPF that should be filtering the exhaust, and an EGR that burns some soot in the engine. Both of those could be close to "full" and failing to eliminate the soot, though you have not gotten any engine warnings.

Follow the suggestion of checking the air filter and also follow the mechanic's advice and drive back home. You may discover that the soot condition disappears. If it doesn't, follow up with your home town service department.
Larry, Eileen, and Finley
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Old 10-22-2021, 11:49 AM   #5
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One other possibility....a B20 or higher blend diesel can cause excessive soot. When we switched our fleet to a +B20 blend our ISX's ran a little "sooty". I would add some diesel kleen to your next couple tanks of fuel and monitor.
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Old 10-22-2021, 12:39 PM   #6
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There's occasions where you can drive through dusty/dirty conditions and produce a film that sticks to the toad, but isn't necessarily greasy. If you've ever lifted your engine door and washed the back side of it, they get filthy with the same type of engine grime.

I see you're on a Freightliner chassis..... open the engine bay and look at the engine fan blade.....if it's greasy, you have a leaking engine fan gear box vent tube. That can produce grime.
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