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  #41  
Old 10-12-2017, 05:52 AM
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rjcthree rjcthree is offline
 
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Location: Bay Village, OH
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Default filter shrank - in three hours

I had 25H TT on my filter before needing to do my condition inspection. I removed the filter which fit just fine, it did not snap off or anything odd. It sat for a couple hours, still fine. I washed it (K&N filter wash) , set it out to dry (breezy sunny day after a gentle air blow off). Was wrapping up and pulling stuff in to find one side of the filter had shrunk significantly, diametrically, over three hours of drying time. It looks like a trunchated cone now. I can't say if just letting it sit would have caused the same shrinkage, but I'm suspicious of the washing process. I'll go to blow-off/shop vac/re-oil for regular condition inspections now, and a periodic replacement (3 years? 5? Depends on degradation or deformation) rather than washing.
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  #42  
Old 10-12-2017, 10:32 AM
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Location: 57AZ - NW Tucson area
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Quote:
Originally Posted by rjcthree View Post
I had 25H TT on my filter before needing to do my condition inspection. I removed the filter which fit just fine, it did not snap off or anything odd. It sat for a couple hours, still fine. I washed it (K&N filter wash) , set it out to dry (breezy sunny day after a gentle air blow off). Was wrapping up and pulling stuff in to find one side of the filter had shrunk significantly, diametrically, over three hours of drying time. It looks like a trunchated cone now. I can't say if just letting it sit would have caused the same shrinkage, but I'm suspicious of the washing process. I'll go to blow-off/shop vac/re-oil for regular condition inspections now, and a periodic replacement (3 years? 5? Depends on degradation or deformation) rather than washing.
The certified K&N filters are sold as Challenger products. This is a link to their cleaning instructions. No mention of blow drying -

http://www.challengeraviation.com/Il...structions.pdf

The Challenger filter for my Tiger has the original K&N part number on it - 60's era Dodge slant 6 I believe - and an extra stamp of "FAA-PMA" on the rim.
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Last edited by az_gila : 10-12-2017 at 10:34 AM.
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  #43  
Old 10-12-2017, 01:00 PM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by rjcthree View Post
set it out to dry (breezy sunny day after a gentle air blow off).
The K&N cleaning instructions say "After rinsing your filter, gently shake off the excess water and only allow filter to dry naturally. Do not apply oil until the air filter is completely dry."

I admit that "dry naturally" can have many different meanings (the sun and wind are natural), but my interpretation has always been to do nothing to artificially accelerate the drying process.
The filter media is cotton. It will shrink just like a 100% cotton shirt will.
If you do anything to accelerate the drying process, it will shrink that much more.
I always do the cleaning immediately after removal and then set it aside on my work cart to let it air dry over night. They can be reinstalled immediately after being oiled.
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  #44  
Old 10-12-2017, 01:09 PM
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I bought a new filter at the first CI. I then cleaned the old filter and let dry as Scott suggests, in the hangar in free air. When dry, after a couple days, I put it back in the box until next year. I then oil the spare and install it (if it is new it is pre-oiled). At the next CI, repeat.
My two filters have lasted 750 hours total and more than ten years with no shrinkage..
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  #45  
Old 10-12-2017, 06:51 PM
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rjcthree rjcthree is offline
 
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Default Blow off as root cause?

So the feedback is blow drying is somehow the cause of the shrinkage. I understand the cotton consideration. The shrinkage is diametrical, not in height, and only on one side. I've not been able make these elements come together with blow drying as a contributor. I'm suspect of the washing solution as a contributor for the same reason now too. A lunchtime Ishikawa diagram, maybe, get everything on paper. I'll report back after I deconstruct it, maybe the rubber returns when free of the cotton. I'm curious about the durometer, and if there's a difference top to bottom. If nothing else, it's an excuse to goof off in the materials lab at work.
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