The International Cessna^® 170 Association

Found copious quantities of exhaust gas entering the cabin. I would suggest carefully inspecting the muffler tail pipe connection.
This aircraft had been modified to incorperate Benham's tail pipe extensions. The installer is unknown and I do not know if the tail pipes are original Benham.

The tail pipe was crammed way too far up on the muffler tail pipe.
The slits were too narrow, the clamp too weak and the tail pipe oversized. The pipe clamp could not possible tighten the muffler/tail pipe connection. The tail pipe was crammed so far up on the muffler that the tail pipe was even with the muffler heater shroud.

No harm was done, but it was scarry as to what could have happened.

Ralph

Ralph, I take it that "cramming the tailpipe too far up the muffler pipe" caused the exhaust gasses in the cabin and the problem has gone away ? There are numerous causes for exhaust gas in the cabin but I never heard of that one before.
Rudy

I agree, Rudy. It's unlikely the connection at the muffler/tailpipe is the source (at least in flight.) That area exits below the fuselage due to the pressure flow in the cowl, ...and the air pressure inside the heater muff exceeds that of any leak.....it will force any leak downward and overboard. All that gas, plus that leaving the tailpipe normally can certainly find it's way into the cabin from the tailcone, the landing gear leg area, and from belly mounted beacon areas. (You might want to do a search on this subject, as it's been discussed/found before.)

Gentlemen,

I was there, I corrected the discrepancies, it corrected the problem.

It can happen, be careful. The two primary culprits were the cramming of the tail pipe too far up and the loose fit of the tail pipe connection.

The oversized swadging is what allowed the whole sequence of events. The oversizing made it possible to cram the tail pipe up too far and the slits too narrow to allow proper clamping action.

Be careful, it can't happen!.

Ralph

Not disputing a successful repair, Ralph. Just curious if I understand the situation. If you are talking about the tailpipes not having an air-tight connection at the stub-exit of the muffler....then I wonder how that got into the cabin? Seems to me, it either got there thru a pathway that is still available to the exhaust leaving the tailpipes below the cowl...... OR the firewall/cabin heating system has/is allowing engine compartment air into the cabin. In such case simply tightening/sealing the tailpipe-to-muff connection is unlikely to rid the cabin of all CO....don't you agree?

kimble wrote:Gentlemen,

I was there, I corrected the discrepancies, it corrected the problem.
.................................................................

Ralph

Who you gonna believe, us "experts", or your lying eyes?

It sounds like the leak was right at the junction of the tailpipe/muffler,I can easily see how the exhaust gases could get into the cabin-heat system via the heat muff-- "higher pressure" or no.

Eric