shrunken K&N filter

Re: K&N filter # E-3450 in 360 fab box. @ 600 hrs.

Durring this last condition inspection cleaning & re-oiling the filter, I noticed it didn't fit into the fab box like it orginally did. What? Checked the specs on the K&N filter web site.. it was smaller.. It fit correctly when first put together & didn't notice this on any earlier inspections.. So, ordered a new one from Van's... New one fits as it should.. Also orginal one was not quite as tall as the new one hence, maybe not sealing up against the top plate quite right... I can understand that, but why it shrunk in diameter..?
Wonder if anyone else has this happen too, or did I miss the 'replace after blank hours' instruction...?
Sheldon

Orginal filter


New filter


About 1/16 inch shorter in height, more in some places

solvents?

Could it be how you are cleaning the filter?

Same Here

I noticed the same thing in my RV-8 with an O-360 and Vans FAB. The original KN filter gradually shrunk over its service life. The shrinkage was mostly in the diameter, but a little in the height. The wear marks in the FAB tell the story. Sorry no pics, but I suspect this is the nature of the beast. The filter was replaced at 1000 hours, a reasonable service life in my opinion. When compared side by side, the 1000 hour filter was much smaller than the new unit and the new unit sealed much better.

I clean the filter using K&N sray cleaner per the instructions.. rinsing in water & letting it dry...

Ok... the instructions on the K&N cleaner bottle says 'excesive heat will shrink the cotton fiber media'.. guess drying it outside in the Az. heat a no- no.. although it wasn't in direct sunlight.. Might be the answer.. Anyway, new one in place...

Mine shrunk in diameter, making it a bear to clean and reinstall after 6-8 years. $20 and a dab of RTV later, I replaced it with a new one. I figure it is an item on the "replace as necessary" list.

Me too!

I thought it was my imagination. But, I remember initially it was a tight fit in diameter inside the fab. But, after the second cleaning per instructions and drying overnight inside the house, it is way smaller.

100ll

Shrinking filters is a common problem. I think the rubber in the filter is not compatible with 100LL.

...just want to throw in a word of caution here...and there are other threads that address this...

Be very careful about using rubber seals, gaskets, etc. in the FAB to tighten up a shrunken filter. Loose stuff can get sucked-up into the carb & the big fan up in front of the plane stops turning.

'Cotton fiber media' (per K&N)... wet it, dry it.. cotton shrinks.. If it does after couple (or more) cleanings & doesn't fit right, time for a new one... cheap.. Cheaper via Van's than at K&N's web site by $7.54...

yup they shrink

I have had several K&N filters in vehicles over the years and they do shrink over time.

K&N Filter Problems

I too had the shinkage issue. But over the course of 6 months, the loose filter litterly wore through the airbox! It had been moving around due to the shrinkage..
I had to re-fiberglass the inside/outside of the airbox bottom to correct the wear issue.
So be sure to check your airbox for wear.....

chuckwn said:

I noticed the same thing in my RV-8 with an O-360 and Vans FAB. The original KN filter gradually shrunk over its service life. The shrinkage was mostly in the diameter, but a little in the height. The wear marks in the FAB tell the story. Sorry no pics, but I suspect this is the nature of the beast. The filter was replaced at 1000 hours, a reasonable service life in my opinion. When compared side by side, the 1000 hour filter was much smaller than the new unit and the new unit sealed much better.

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