Found the source of CO in the cockpit

[benyflyguy]

I use a sensicor CO detector in our club 182H. Was getting occ CO readings 5-10. Nothing too bad. Thought it was baggage door seal letting some pull in through the slipstream. Last two flights I noted it really jumped. 20-30ppm. Plane went into annual with that as a squawk.
Two small cracks in the shroud and the baffling inside is gone. Vanished!!! How the heck does that happen. Didn’t get a price on that yet but I’m betting pricy.

 

[Initial Fix]

Glad you found that. CO poising isn’t how I’d like to go!

 

[Sinistar]

If you are talking the long since vanished spark arrestor...you have a seaplane muffler now I think they get so darned hot so many times along with who knows what else and rust and they just eventually go to heaven.

We had a similar crack that had just started and was noticed during another mx event.

 

[Domenick]

The baffling disappears due to corrosion and erosion. It starts spewing flakes and eventually chunks. All the perforations make for a crumbly tube. The photo is not the baffle, but demonstrates the same effect on the stacks.

 

[Let'sgoflying!]

It didn’t always leave in powder form; have heard of large chunks blocking the outflow.

 

[Clip4]

View attachment 102627 I use a sensicor CO detector in our club 182H. Was getting occ CO readings 5-10. Nothing too bad. Thought it was baggage door seal letting some pull in through the slipstream. Last two flights I noted it really jumped. 20-30ppm. Plane went into annual with that as a squawk.
Two small cracks in the shroud and the baffling inside is gone. Vanished!!! How the heck does that happen. Didn’t get a price on that yet but I’m betting pricy.

None of you members ever complained of poor cabin heat?

 

[Dan Thomas]

None of you members ever complained of poor cabin heat?

It won't affect the cabin heat. In fact, if the leak is big enough it will increase the cabin heat, just before the crash

 

[Dan Thomas]

Canadians have a blanket AD against all aircraft that use the exhaust system as a source of cabin heat. That AD came about as a result of accidents caused by CO poisoning. And because of that annual/150 hour AD, I have found numerous cracks in mufflers and pipes. In fact, at any inspection, the first things I looked at on the engine were the exhaust components. Defects were common enough that I wanted to know about them immediately so I could get parts coming. That exhaust system is red-hot at full power, and has vast quantities of corrosive exhaust gases surging through it. It's a wonder that thin stuff lasts as long as it does. Very unlike automobile exhaust systems, which is a built of much heavier stuff and where full power is rare and brief.

Accidentally turning the mags to OFF during the runup, then back ON without closing the throttle, creates an explosion in the system that can crack things, too.

http://www.aeroelectric.com/Reference_Docs/Cessna/cessna-maintenance-manuals/Cessna 172 Parts Catalog (1963-1974).pdf