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Grumpyjoewv · 12-05-2022, **(Subject: Very strange smell. Stumped )**

06 W9 ISX

I’m totally stumped. I’ve been getting an exhaust type of smell in the cab. Fairly strong. We’ve replaced the entire exhaust from the turbo to the stacks except for the muffler. New Y pipe, all new flex pipe, clamps, etc. Had two minor leaks at the manifold and after a quick re-torque, no more leak. There are no leaks anywhere. Here’s the first weird part. It only happens when the outside temp goes below about 35 degrees. The even stranger part is, it gets worse after the truck is parked and the engine is shut off. It finally gets so bad that I have to roll the windows down and open the sleeper door and grab the dog and get outta the truck. After an hour or two there’s no more fumes. What am I missing?

Waterloo · 12-05-2022, **(Subject: Very strange smell. Stumped )**

I have exhaust gas that enters through the shifter boot, weed burner. I installed a new boot, as it was torn, still had the issue. I put a worm gear clamp around the top of the boot where the shifter exits into cab, no more fumes in the truck.

Grumpyjoewv · 12-05-2022, **(Subject: Very strange smell. Stumped )**

I have stacks but that doesn’t mean much at this point. I never even thought about the shifter boot but I definitely have some serious air coming in around mine. I’m gonna block it off and see if it helps. I’ll let ya know in a few minutes. Thanks man

Grumpyjoewv · 12-05-2022, **(Subject: Very strange smell. Stumped )**

Waterloo, you have saved me once again my friend. This truck has about a 12 inch gear shift extension and one of those zippered covers. I would’ve never in Hell thought about checking it. Pulled the cover off and sure enough the damned boot has a hole in about the size of a quarter. I wrapped some rags around it and the smell all but disappeared. I’ll grab a new boot somewhere today. I’m still baffled because it only does it when it’s fairly cold outside. I’m thinking it’s always there but the cold air just makes it more noticeable. Thanks buddy!!!!

Grumpyjoewv · 12-10-2022, **(Subject: Very strange smell. Stumped )**

Well, I replaced the boot and it definitely helped, but I’m still getting the smell. It only happens at night when it starts getting chilly outside and I’ve noticed now it’s worse while I’m sitting still. With the engine off, it gets worse and worse for about an hour and then it’s gone. I’m thinking it’s gotta be a gasket expanding and contracting.

Waterloo · 12-11-2022, **(Subject: Very strange smell. Stumped )**

(12-10-2022 )Grumpyjoewv Wrote: Well, I replaced the boot and it definitely helped, but I’m still getting the smell. It only happens at night when it starts getting chilly outside and I’ve noticed now it’s worse while I’m sitting still. With the engine off, it gets worse and worse for about an hour and then it’s gone. I’m thinking it’s gotta be a gasket expanding and contracting.

I was working on my truck a few years ago, and had some of the exhaust off, front and back of the turbo. I found a connection that did not have a gasket, that silver one with the slight concave. I called the dealer parts dept and they insisted there is no such gasket, it is a Cummins part, 5 inch, silver fibery thing... I would start there, from the turbo back. I will see if I have the Cummins part number for that gasket. Odds are, if that truck of yours was in the shop and they touched the exhaust, those gaskets were never replaced. Here is the Cummins part number, 2866337. There are normally at least two, possibly three between the turbo and the first can.

I am currently fixing a bad delete on a truck right now, and found those gaskets missing. Also, in the elbows around the turbo, there are o-ring gaskets at the metal to metal connections. I replace mine every few years, as they do get brittle. I apply anti-seize, the silver stuff, to help hold them in place, and extend their life.

I would get under the cab too, any slip joint connections or flex pipe, and look for holes in the bottom of the cab, especially if you have an APU installed. It could be something as simple as a hole that was cut, not used, and not plugged. Or, one of the factory plugs was removed and never replaced. Look at the firewall too, where the bulk of the wiring enters the cab...

Right now, I would bet it is one of those 5 inch gaskets that has failed, or was never installed if any exhaust work was done.

marek4792 · 12-11-2022, **(Subject: Very strange smell. Stumped )**

Not a solution, but I would definitely get a co2 detector for situations like these and in general.

Rawze · 12-11-2022, **(Subject: Very strange smell. Stumped )**

pressurize the entire engine and exhaust system. Put an EVAP machine test kit on it ... . fix any and all leaks.

Even I own an evap machine and pipe plugs .. why can't a typical repair shop do this ??.

here is an older post on testing the engine this way: http://rawze.com/forums/showthread.php?t...21#pid8321

Grumpyjoewv · 12-11-2022, **(Subject: Very strange smell. Stumped )**

Well I found one major leak. Rawze is this one of the connections you were talking about that has a gasket or an o-ring? It’s the clamp on the end of the exhaust manifold just above where the EGR cooler used to connect. Check picture below. Also found that my heater box has serious rust issues on top. Couldn’t be seen from the ground so I’m guessing this might be where the fumes are coming in.