The International Cessna^® 170 Association

Can’t get the exhaust leak to stop under clamps. My mechanic and I just put the new parts on for the 3rd time (he’s giving up) and the cabin heat still leaks CO although not near as much. Thanks goodness for my CO detector. Let me tell you something, I am such a believer in having a detector. I’ve used it to trouble-shoot the whole way and if it hadn’t been for the detector, the job would have been written off as a success the first time. They finally asked me to prove it’s calibration, so I went over to the fire station. We put the fire chiefs unit, along with mine, up to the exhaust of a fire truck. Tracked perfectly, although mine lagged a bit not being quiet as sensitive.
As for the muffler replacement:
First time – mechanic surprised me and did it himself, no tape or anything (just like it came off). Pegged High CO.
Second time – I insisted on Victor tape, we did it, Pegged High CO. However tape could have been torn some while trying to squeeze clamps on.
Third time – I dropped the riser’s down without taking nuts completely off, so we could maneuver clamps on without tearing tape. The mechanic, not a Victor tape fan anymore, made 3 separate wraps around each joint with aluminum tape. He was determined that it wasn’t going to leak anymore. Then we clamped it, easier this way, and bolted back to engine. Went flying – at first I thought we had it, then the CO creped to 27-30 ppm, shut Cabin Heat off, went back to 0. Flew a bit, opened Cabin Heat, creped up to 60-70, shut off, back to 0. At least we can warm up before 30 ppm now. However I am TO’d.
Was brainstorming about how to get a welder in there and weld each riser / muffler joint permanent. Now I am leaning more towards JB weld. HELP? I want a permanent solution. For safety reasons!

FWIW, it's been speculated that the reason that 170 crashed into the salt water near here a month or so ago was CO poisoning of the occupants,as there had just been some repair/replacement of the exhaust system. Could be that,or any number of other causes/factors.
I have a friend that works for the FAA,I'm hoping to hear from him what the autopsy's reveal. Meanwhile,I urge everyone to have a CO detector on board. I use those $6 cheapies,but I think they work pretty well if they're fresh--they have a 90-day service life,as well as an expiration date.

Eric

I talked to one of the inspectors who inspected the wreckage.

One of the muffler assy's was found in, shall we say, horrible
condition (it was implied that it was not a result of crash
damage).

Long story short, I agree with Eric. Get a good detector and
watch it!

Bela P. Havasreti
'54 C-170B N170BP

They stated on the TV news that it may have been CO poisoning as NTSB discovered a damaged muffler. This was while they were showing a film of the airplane being yarded outa the water by the tail,with the engine broken clean off the front of it! Duh---if the muffler wasn't damaged,it'd be a miracle!

Eric

Dave, I wonder if your mechanic has "pressure-tested" your muffs or tried the soap-and-vacuum method of leak tests? This is frequently done with Janitrol cabin heaters and such. Soap suds are blown thru the exhaust in reverse via a shop vacuum exhaust, to detect leaks. I'm suspicious of areas other than your riser-to-muffler connection as being the source of CO.
Are your shroud seals in place and in good condition? These are sheet-metal "skirts" on the muffler inlets just below the riser connections.
The Victor tape will appear damaged upon disassembly (after it's been vulcanized by heat) but is unlikely torn during assembly. Two wraps are usually sufficient. Aluminum or metal tape is completely useless as it blows thru in only a few minutes. I would not advise JB Weld as it's actually an epoxy (and flammable at high temps.)

zero.one.victor wrote:They stated on the TV news that it may have been CO poisoning as NTSB discovered a damaged muffler. This was while they were showing a film of the airplane being yarded outa the water by the tail,with the engine broken clean off the front of it! Duh---if the muffler wasn't damaged,it'd be a miracle!

Eric

Only passing along what the inspector said. He said there
were "indications" that something had gone wrong with one
of the mufflers prior to the aircraft striking the water. Guess the
right thing to do is wait for the NTSB report to be published
before we speculate much more....

Something else interesting he mentioned is the magnesium
accessory case and pan were basically gone (that's how
quick that stuff corrodes!). FWIW, the engined still turned
over freely.

Bela P. Havasreti
'54 C-170B N170BP

Eric,
I just got in from Palestine Texas, where I inspected Randal's fine looking 170. Really nice! I tried to buy one of those yellow dot cards for the plane, but our airport was out. I'm going to put a new card in and test how long it takes it to turn black compared to my known metered source.
Gahorn,
You might be on to something, for I've been wondering the same thing for a while. We taped off the exhaust and put air pressure to the system (but that was a lot more psi). Then we squirted soapy water on the clamps to watch the bubbles. We did this after the 2nd attempt failed and after the 3rd re-do, before cranking up. The last time it only leaked on the middle and back one and not much. Since this was a lot more pressure from his compressor, we figured this might be good.
One more thing, when I slow down and enter down wind, even with Cabin heat off, I get a little chirp of 15-25 ppm. Other than that, I never have CO with Cabin heat off. I started noticing this with fresh air off, I don't think it's coming in with fresh air blowing. The flapper valve in the fire wall doesn't seat real tight, needs new rubber for tight fit.
NOW - About these shroud seals? I'm not picturing having something like that and I've been thinking there should be. I'd better go find a parts book. I think I'll take it a part one last time and wrap it with the Victor myself ( maybe up at the Petit Jean Fly-in ) now that I've figured out to loosen the top nuts. Shroud seals, hopefully that's the ticket.
I just had a tail wind push me home at 125 kts, that's 33kts faster than I'm used to. Man, that was nice! When I took off into the 11 kt wind, I climbed to 6000 feet in - well ya'll wouldn't believe me, so lets just say my usual 1000 fpm was easily passed. Then to finish off a great day, back in the hanger, I rammed my aileron into the Saratoga Prop.
Dave

zero.one.victor wrote:FWIW, it's been speculated that the reason that 170 crashed into the salt water near here a month or so ago was CO poisoning of the occupants,as there had just been some repair/replacement of the exhaust system. Could be that,or any number of other causes/factors.
I have a friend that works for the FAA,I'm hoping to hear from him what the autopsy's reveal. Meanwhile,I urge everyone to have a CO detector on board. I use those $6 cheapies,but I think they work pretty well if they're fresh--they have a 90-day service life,as well as an expiration date.

Eric

I just heard from a guy (who heard from a guy,who heard......) that the autopsy revealed CO poisoning. It's not official,yet,but it should sure make everybody think about having some type of CO detector on board. Like they say,it's an insidious killer.
( Webster:"insidious: operating or proceeding inconspicuously but with grave effect". )
What a terrible tragedy,especially since it could have been avoided.

Eric

Three possibly overlooked sources of CO are:
1. At the left wing strut lower end seal. Look at the exhaust stains and you can see where, expecially in slow flight, exhaust can enter the cabin at this location as well as at a bad left cabin door seal.
2. At the tail empennage. The openings near the horizontal/vertical tail and tailwheel can allow exhaust to enter the tailcone where, due to air flows, it moves forward into the cabin.
3. At a lower belly-mounted beacon/strobe. Exhaust is deflected by the beacon upwards into the tail cone, and again, it moves forward.
The rear hat shelf usually has nothing other than fabric between the cabin and tailcone. Some owners, including myself, installed a solid sheet of 2024-T3 Alclad there, attached with PK screws and Tinnerman nuts (or not), and soundproofed with adhesive, foil-backed foam soundproofing. This stops most of the forward airflow coming from the tail. Side-benefits: Cabin heat works better. Rear seat noise level drops, especially during taxi. (Cable slap and oil canning noises during taxi across pavement strips can be pretty distracting to a passenger not wearing hearing protection.)

I saw an early C-172 with a "Bartone" type exhaust pipe system except that the tail pipes extended down about eight or ten inches. Perhaps a set of this kind of pipes wound improve the dissipation of the exhaust concentration just under the fusealage.

I was looking in Search for Bartones and read these last few post!
Here comes winter again and how many 170's are out there without a CO Monitor? They ought to be mandatory equip list!!!!!!!

With that said - How come after all the past discussions, any member or visitor of the 170 Club can't simply log on to this site and find out what monitor to get & where to send the money for purchase? Is this a secret? What?
And people have asked! Don't tell me to buy Canadian Made, tell me the model number and brand. This is a matter of life and death and not something owners should have to put a lot of research and effort into if we already know what works!

I would like to see our customer recommended Aircraft CO Monitors in a location, where it can easily be seen. What do you think about this spot:
Forum - Hanger - and put it above or below -

Sticky: Tailwheel Tie-Down Eyebolt/ Tow Adaptors Offer
Sticky: CO Monitor Consumer Report

AIM, model 935, Hand Held, life 3 yrs, ~ $70.
Sporty's, CO Detector - $49, 9 volt battery last 1 yr..
AeroMedix, Senco Model One for $75
AeroMedix, CO Expert Model 2002 for $100 ~5ys

are some that we've discussed anyway!

I use the cheapie disposable "Deadstop" brand detectors. Chief Aircraft has them on page 100 of their volume 24 catalog,which I just got not too long ago in the mail. Part number DTR CO...$6.50. They're good for 3 months after opening, and also have an expiration date so they must have a limited shelf life.

Eric

AR Dave

I understand what your saying and there is probably a better way to list such things so they may be more easily found. Not sure an individual header nder forums is it though because it the list could get real long. I'm not making light of the CO issue but many 170s have and will conitnue to fly successfully without CO detection. If this safety issue was an absolute "your plane will blow up if you do this" it indeed should have a header in red.

If you want to post something that you want people to be able to find don't bury it isn a post with another subject. Your post and CO dectector listing is in a thread labeled "Muffler Problems". They are related but it would be better for searching if the list was under its own subject labeled CO detectors. You would also want to put the words Carbon Monoxide in the texted in case someone was searching on that. This isn't the first nor the last time this time something worth finding will be buried in an unrealted subject thread.

but many 170s have and will conitnue to fly successfully without CO detection.

And then there's the occasional 170 like the one we were discussing in this topic, that flew successfully without CO detection until it was detected in the Autospy.
My point was - to Not put it in a post that needed a Search at all. I think it is important enough that it should remain fixed on the front page or somewhere for those to see whom missed the discussion way back. Not a CO discussion again, just maybe post the detector and if you're satisfied or not.
Also I agree, there are 170s with CO in the cabin and it isn't being detected.
Anyway -