AHA! The GREAT George speaks Glad I waited on the silicone sealing project. I am a bit confused though, as I see quite a few airplanes with what appears to be silicone sealer on them in places, and my own 170 has a spot or two of the stuff. The FBO seals the removable fuel tank covers on his aircraft with what he says is silicone sealer Is there indeed no SAFE flexible sealer for aircraft use I suppose I can cut up an old car inner tube and make seals this way, but then what type of adhesive would be safe to use on the aluminium Comment in a new subject thread if you wish as we are getting a bit off topic here.
There are appropriate RTV-type aviation sealants, and Pro-seal, etc. may be used. But I'd be cautious about sealing up landing gear/strut entry's with sealant. It will not allow water to "wick" away from the area like a gasket will, and will encourage corrosion.
Some thoughts on sealing up the landing gear entrance to the fuselage.
Part of my annual is checking the landing gear wedge bolts to see if they have loosened up. In the past I have found that a bolt was missing and on occasion they have loosened up.
There is suppose to be a removable seal behind the landing gear fillet plate.
I don't think I wouldn't use any permanent sealant in this area.
Just my input.
Bob
Well I suppose I am not going to worry about sealants or gaskets either at this point. I just went up yesterday for the first time since I got the $49 CO detector from Sporty's. The heater put out so much heat that I thought my shoes were going to melt Things stayed nice and toasty in back for my 2 year old, and not one CO alarm from the detector. I can only assume that there are no leaks in my right muffler and whatever seals are still in place around the gear and strut entrances are doing OK....even thought I can see daylight if I look at the right angle.
Glad to hear of the wedge bolt problem though, and will make sure this gets checked on annual next year...actually NOT glad to hear of the problem, but happy to be forwarned of potential problems in the area.
John.... I have checked the gear wedges for the last two years. The first time a bolt was missing and was probably missing for awhile, the next year two bolts needed to be tightened up.
I check them with weight off of the gear.
Bob
After reading this thread I bought a CO detector- a Senco Model One for $75 from AeroMedix. There is a slight exhaust odor in my airplane.
The CO readings on the ground are zero but in flight its 28 ppm with the vents open and up to 57 with the vents closed. The heater does not seem to make much difference.
My IA inspected the mufflers and says they are in good condition. (But he didn't do the soapy water test).
My exhaust stacks only extend about one inch below the cowl so I'm having them extended. I hope that helps. Will report further.
Rudy
Rudy... I replaced my tailpipes with a set from Wag-Aero pg 66 cat no. E-420-000 I installed new clamps at that time also.
I haven't checked this co2 stuff yet
Bob
Bob, thanks- I replaced the clamps but it made no difference. My tailpipes only protrude about 1" out of the cowl which seems shorter than other 170's. (OK no wise remarks, George) -I'm having them modified to be 2" longer. I hope that's enough and that it reduces the CO level. I'll also check the sealing at the gear box.
Rudy
Careful on extending the tailpipes. Not only will it be not legal, extended pipes have been known to contribute to exhaust system cracking due to increased "moment". (The additional weight, and length adds stress during vibration.)
It's unlikely the length of the tailpipes are the cause of exhaust in the cabin anyway.
The likely sources are:
1. Leaking riser flange gaskets.
2. Leaky riser clamps.
3. Leaky exhaust muffs/shrouds.
Since you've eliminated the muffs/shrouds, then look for the first two items. The exhaust in your cowling can then enter the cabin thru any opening, expecially thru your heater mixing valve and any leaks in the firewall (and of course, thru those landing gear legs).
I did extend the tailpipes and it did no good. I also sealed the left gear leg opening- the right one has no exhaust stains. Cabin heat makes no difference- on or off it's the same reading. So maybe that is the problem. The right exhaust muff is new- a year old- and I pressure tested the left one- found a tiny leak in the front riser and had it repaired at an approved shop. I test flew this morning and the readings are about the same-
up to 71ppm in climb with vents open, stabilizes at around 29ppm in cruise. Vents closed it goes to around 50ppm in cruise.
Next I'll seal up the riser to muffler clamps and check those gaskets.
Rudy
Ram Aircraft used to seal up leaky slip-joint clamps with a type of fiberglas/vulcanizing tape. I noticed that at Wally's aircraft supply (WalMart automotive section) that Victor brand of tire repair materials has a display that included a similar product advertised to seal mufflers with holes in them.
After determining from another reliable repair station that such was not unheard of in airplanes, I bought a package of it, and wrapped two wraps around each riser-to-muffler joint and clamped the clamps back down. As per the instructions, I ran at high idle for a few minutes to "set" the tape and then let it cool. I then flew the airplane for about 30 minutes and returned to find the stuff had vulcanized itself beneath the clamps and sealed it all up perfectly.
The clamps were difficult to install over that tape, and anyone who's ever done this sort of work knows that it's a tight fit anyway. But I'm happy with the job and the results. I purchased brand new Knisely risers before I did this, and used all new stainless bolts/nuts etc. I don't want to have to try to seperate them from the muffs anytime soon because I have no idea how much trouble it may or may not be.
George, thanks for the advice on the sealing material. My AI told me he uses aluminum hi speed tape inside the clamps on his 210. (Why didn't he seal mine when he installed the mufflers?) That's what we'll try tomorrow- I'll keep everyone posted on the results.
Rudy
After much trial and error , 10 test flights over three days and some good advice from George, I finally located and corrected the source of the CO in the cabin of my 170B.
First, what DIN'T help: extended stacks, new cabin heat gate valve, sealing the muffler-to-risers, sealing (with tape temporarily) the landing gear to fueslage opening and empennage to fuselage gaps.
I was getting CO readings up to 71 in climb with vents closed, around 45-50 in cruise with vents closed and around 30 with vents open.
The main culprit was a gap in the belly aft of the baggage compartment where a Whelen strobe had been (badly) installed by a previous owner.
At some point in its life this was also where a large old-fashioned ADF loop had apparently been. (Not the WW2 type but a streamlined fairing about 2 ft long and 10" wide)
When all openings were taped (LH door, landing gear to fuselage openings, all belly openings, belly inspection panels, empennage to fuselage joints) the CO readings were low- vents open- 0, vents closed 14.
After removing the tape only from around the strobe and jiggling the strobe a little the next test flight showed a jump to 93 with vents open and 71 with vents closed. This clearly showed the source of the CO.
I removed the strobe and installed an aluminum plate over the opening. I also placed a thin one half inch strip of air conditioning foam seal around the pilots door frame.
The test flight this morning gave readings of 0 with the vents open and 14 with the vents closed.
I still hope to get rid of the remaining CO but am happy with the improvement.
Rudy
PS to previous message: I also disconnected the hoses and taped off the cabin air box on the firewall and determined this air box was not a factor.
Rudy
Glad I waited on the silicone sealing project. I am a bit confused though, as I see quite a few airplanes with what appears to be silicone sealer on them in places, and my own 170 has a spot or two of the stuff. The FBO seals the removable fuel tank covers on his aircraft with what he says is silicone sealer 
Is there indeed no SAFE flexible sealer for aircraft use 
I suppose I can cut up an old car inner tube and make seals this way, but then what type of adhesive would be safe to use on the aluminium 
and on occasion they have loosened up.