Exhaust smell in the cabin when stopped

[Boboutside]

Need help. I have a 2020 Silverado 1500 5.3. I have a strong exhaust smell coming from the vents and also in the engine compartment when not driving or driving slow.  Checked with a carbon monoxide tester a friend had from his firehouse. Seems to be at high levels passenger side of the engine. I’ve had the exhaust smoke tested 2x and went as far as installing a new exhaust manifold on the passenger side. The problem still exists. No visible signs of a leak. No warning lights or codes. Can anyone out there help?  I’m already  in over 1k and frustrated. Truck runs great at 88k and no loss of power or rough idling.  

[Kevin0311]

Not sure if the newer trucks have a crush copper ring where the y pipe and maifold connect but my14 had smell when very slow or stopped and installing a new one fixed that. Was a $10 part

 

https://www.gmpartsdirect.com/oem-parts/gm-exhaust-seal-15077362?c=Zz1leGhhdXN0JnM9ZXhoYXVzdC1jb21wb25lbnRzJmw9MTcmbj1Bc3NlbWJsaWVzIFBhZ2UmYT1jaGV2cm9sZXQmbz1zaWx2ZXJhZG8tMTUwMCZ5PTIwMjAmdD1oaWdoLWNvdW50cnkmZT01LTNsLXY4LWdhcw%3D%3D

 

2020 has the same

Edited November 3, 2024 by Kevin0311

[Boboutside]

Thanks for the advice. I will double check that as well. 

[Steveo1]

Same problem here.  I Also have a 2020 Silverado 1500 5.3.  Just smoke tested it this morning and no luck.  Its been going on for months.  Have you had luck with anything else?

[marpel]

Same thing happened with my '12 6.2L Sierra and now my '22 6.6 Sierra HD does the same thing. Problem is it only happens at certain times and is difficult to understand exactly under what conditions (speed, wind direction etc). With the '12 sometimes even had to open the window, and turning the circulating air to in-cab seemed to help a bit, but those are a pain to do every time it happens. And this sort of thing shouldn't happen at all in this day and age (but I suppose that could be said for a lot of issues with these trucks). Was considering trying a cabin carbon filter to see if that helps. What does the linked ring actually do to stop the smell.

[Kevin0311]

the ring i posted is a copper crush gasket, i would consider one time use, takes up the void from the collector at the manifold to the Y pipe.

[marpel]

Kevin0311,

 

Thanks for the info.

[Dan Spangler]

On 11/3/2024 at 10:10 AM, Boboutside said:

Need help. I have a 2020 Silverado 1500 5.3. I have a strong exhaust smell coming from the vents and also in the engine compartment when not driving or driving slow.  Checked with a carbon monoxide tester a friend had from his firehouse. Seems to be at high levels passenger side of the engine. I’ve had the exhaust smoke tested 2x and went as far as installing a new exhaust manifold on the passenger side. The problem still exists. No visible signs of a leak. No warning lights or codes. Can anyone out there help?  I’m already  in over 1k and frustrated. Truck runs great at 88k and no loss of power or rough idling.  

I had this very same problem on my 2010 GMC Sierra 1500 and now it's starting to happen on my 2018 GMC Sierra 1500. On my 2010, it ended up being stuck valves due to the AFM causing gunk build-up, causing back-flow through the intake into the engine box. I ultimately had to swap out that engine.

[IOMTT]

Same thing. It smells like CRANKCASE fumes to me. 
2020 5.3 180,000 mi, uses 2 quarts in 7500mi

[bbqn]

Same problem.

2018 Sierra 5.3, 60k. Smells like rich exhaust coming thru vents when stopped. Under the hood also.

Exhaust at the tailpipe does not smell like this. So I figured it must be before the cats. 

 

Digging around I found an exhaust leak on pass side where manifold attaches to y pipe. This is where that seal Kevin mentioned above is located. That small seal may not fill the void where I feel exhaust coming out.

Also, I found a good size dent in the y pipe from a chunk of steel I hit that a truck kicked up. My flange may be bent.

Time to take it apart and see what's going on.

 

[johnnyquick]

Check PCV as well guys, on our performance rigs when boosting is increased we need to vent the crank case out behind the passenger compartment.

I know you are likely running stock CC pressures but it is a quick and easy check.

[bbqn]

Good advice.

The PCV was the first thing I checked. Pulled air box off and checked all lines and connections. All good.

In my case, I can feel the exhaust coming out of the connection between the manifold and y-pipe. Bolts are tight.

May try J-B weld 37903 before taking it apart.