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Installing Nylo-Seal fittings to instruments

ArVeeNiner

Well Known Member
Hi all:

I'm installing some Nylo-Seal fittings into my Dynon, airspeed indicator, VSI, and altimeter. The "T" type fittings tighten just fine but I have a problem with the straight fittings. These are P/N 268-N04-02 at Aircraft Spruce. They seem to not get very snug. I swear I was careful not to over tighten them but they turn with much less force than I would have imagined. In fact, when snuggin the tube to Nylo-Seal interface, the Nylo-Seal to instrument interface turns a bit as well. I've pulled a couple out and looked at the threads and they look ok. I also put some Teflon paste at each joint.

What am I doing wrong? I would imagine that I could expect leaks at the Nylo-Seal to instrument interface? Any tips on installing these?

Since I have a slider, I sure don't want to have to shimmy up there to fix future leaks.

Thanks!!
 
Is it all the way in.

Make sure you have the tube "all the way in". If you can pull the tube out with a little tug, then it may not be bottomed out prior to tightening.
 
The tubes are fine

The tube interfaces are fine. It's the interfaces between the fittings and the instruments themselves that may have issues. I've used I'm thinking at least 4 straight fittings and they all either have a very low or non-existent "snug point". I've thought about cleaning off the Teflon paste and putting a bead of Goop around the fittings. They will be hard to remove in the future but they would probably not leak.
 
I had almost every

pipe thread on my nyloseal instrument fittings leak! Had to remove them all and use a sealer on the threads. Don't use too much, and not on the first thread (this keeps the goop from getting inside the instrument). The sealer will act like a lube when installing the fitting, so just I just use finger pressure on a deepwell socket to install.

Good luck.
 
Same here, after 3 years all my nylon fittings leaked at the theaded interface to my instruments. They "cold flowed" and became loose. I had to replace them all with brass fittings while standing on my head under the panel. Use Brass now and you will be happier later.
 
Brass fittings??

Where do I get these brass fittings? Are we talking these from AS?: http://www.aircraftspruce.com/catalog/hapages/polyflofittings.php

The plastic "T" fittings that I've used seem to get snug just fine. Only the straight fittings don't get that snug. I'm curious if the leaks that were found later by otheres were with all types of fittings...T's or straight.

Last night I wiped off all the Teflon paste and wrapped the fittings with Teflon tape. The fit was a bit better but I'm still not happy. I don't like the thought of crawling up there after I get the top skin on. Ouch!!!
 
Last edited:
Where do I get these brass fittings? Are we talking these from AS?: http://www.aircraftspruce.com/catalog/hapages/polyflofittings.php

The plastic "T" fittings that I've used seem to get snug just fine. Only the straight fittings don't get that snug. I'm curious if the leaks that were found later by otheres were with all types of fittings...T's or straight.

Last night I wiped off all the Teflon paste and wrapped the fittings with Teflon tape. The fit was a bit better but I'm still not happy. I don't like the thought of crawling up there after I get the top skin on. Ouch!!!

I think any metal 1/8 inch pipe thread fitting will work better than nylon over the years. Some builders have told me their nylon pipe thread fittings worked fine but all mine came loose, straight and Ts. I got my replacement brass pipe to tube fittings at Home Depot in the aircraft section. :)
 
One thing I want to make sure everyone is aware of, watch your fitting torque on the the Tru-trak equipment, mainly the tray mounted stuff and anything else where you are screwing fittings into a plastic/phenolic housings. Go easy on the wrench!! I have found the top and bottom of most tray fittings are very thin and will crack, not enough to be seen by the eye unless you are lookin for them. It will drive you nuts when you get to the pitot/static leak check:mad:. It's that hard to see those cracks. I have found teflon tape to be the best thread sealer but I'm sure others have a better product. Main thing is to keep any sealer/tape debris from the ports in the connectors. BTW, Stein and Safeair sell those nifty push in connectors..they work GREAT...You can also get them from McMasterCarr...but I like to keep it in the family!
 
quick release fittings

I bought mine locally from a business named "Motion Industries". They are a dealer of bearings, rubber belts and lubricants. $3 per fitting + tax + no waiting for FedEx. They also sell 1/4" nylon tube in many colors but 100 feet is the min qty.

Check your local Yellow Pages,
Steve
 
After 11-years of flying 2,159 hobbs hours, I have never had any of the NPT Nylo-Seal fittings leak. As someone else said, always use sealant on the threads. Yes I know that you should not use teflon tape on aircraft but I did on my Nylo-Seal NPT fittings.

There have been NO leaks when the transponder / pitot-static checks are done in accordance with 91.411 / 91.413 every two years.
 
Nyloseal with nyloflow tubing

As I understand tiny little inserts are required with this combo. Part #
259-N-04 I think these keep the softer nyloflow from yielding.

hal
 
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