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2FlyAgain

Carb Debris (a new source...)

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I previously described my rough engine after run-up in another thread.  Opening up the carbs to check them revealed an unexpected source of debris (see attached photos).  I believe that Dean Vogel at Lockwood would joke that this is big enough to have a "part number".   :(

 

The debris is believed to be a piece of the rubber(?) molding from between the airframe and the air intake scoop.  If if one looks inside at the air filter, the material seems to "disappear" at the back of the air filter (right, copilot's side).  This piece was found in the carburetor.  According to the mechanic who pulled it, gash in the tubing was where it was caught in the butterfly valve.  If I had been watching him pull it, I doubt that I would have believed.  I am still dumbfounded.

 

It has been awhile since the air filter was last changed.  But perhaps the molding was damaged during the last replacement and eventually the piece broke loose.  Beyond that speculation, I have no idea why it appeared recently.  The aircraft is a 2005 CTSW that has seen cold winters and hot summers in the great plains.

 

Not surprisingly, the engine seems to run much better now.  Although, I have not yet had a chance to actually fly the plane.

 

I am not a mechanic, so please correct me if my terms are not accurate.

 

 

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I am correct about the origin... The piece was between the frame for the filter and the airframe.  It did not get "past the filter" in the obvious sense.  It may have been caught between the filter and its frame.  Getting past the filter as the filter was being put in place.  It may have been dangling just under the filter for a couple of years and eventually broke loose.  

 

I am open other reasonable explanations...  That is just my best guess.

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I removed all these when the fire wall blanket was put on at my shop. Since this is on the outside of the filter it had to have been loose and the airbox frame  bolted down with this piece already in the inside of the airbox under the filter or it fell in when the filter was removed at one time to look at it. That's the only two ways since this molding is on the outside of the filter. It evidently finally either broke off or was in a position to be moved and sucked in by some air movement.

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cdarza   

image.thumb.png.8bcfb3fb46d0c1008b081511b0bd537e.pngimage.thumb.png.f0331b202ec877d164541c761ae9ebf5.png
Right and Left Carb Bowls :(   8 months and 50 hours since last checked. (These were new bowls 8 months ago that already have corrosion). My last pair was replaced also due to corrosion.   The black specs that look like rubber are actually pcs of dirt.   

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The corrosion is usually water that has been sitting. Unless it gets really bad it won't hurt anything. Most carbs I see have a small spot of corrosion. If it is more than a spot then it can be cleaned up with a scotchbrite pad. I tend to see more of this with 100LL. The 91 oct. with ethanol tends to keep the water in solution and passes through instead of sitting.

 

I had one set of carbs come in from Florida for a rebuild and they were totally thick with white powder. Totally destroyed. I removed all the white powder and the carbs were seriously pitted. The causes was lots of water that sat for a long time.

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cdarza   

Could you clarify for me where this water might be coming from?  That may be a duh question as the answer is most probably the tanks/fuel correct? However, I have never ever seen a droplet or any dirt ever in the gascolator.   So can I assume then that the source of water or dirt is somewhere past that stage?   

I use the aircraft almost every weekend and the fuel I use is 100 octane No ethanol (Petron Blaze 100) which I thought was a better fuel being it had no ethanol  - Should I switch to with ethanol?     

I guess I shall be checking the carb bowls monthly from now on.

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Moisture can come from a poorly sumped fuel delivery tank or almost any source. 100LL will not suspend water so it sinks to a low point. Ethanol fuel will absorb moisture and it just runs through the system. You may see however a small corrosion in almost any carb bowl. I see it all the time. It isn't a big deal unless it is some quantity to it or it starts to pit the bowl.

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It may come from condensation caused by evaporation of fuel in the float bowl. I had the float bowls removed from a CT one day that was running on 100LL. The day was very hot 100° plus, and very high humidity. In a period of about 20 minutes there were several droplets of water in the bowls and the fuel level had reduced by 25% due to evaporation.  

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Anticept   

I could see the evaporation dropping the bowl temperature and the air over it, forcing water out.

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