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Old 07-11-2016, 02:29 PM
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JonJay JonJay is offline
Join Date: Jan 2007
Location: Battleground
Posts: 4,160

Originally Posted by Stoo View Post
It is better to use a pipe die on the fitting rather a tap on the female thread for clocking. It doesn't take much, the anodizing is barely scratched off in a few spots. Way easier to wipe off the male thread than to have to disassemble the master cylinder for cleaning.

Stewart Willoughby,
6 FWF.
Well, that certainly sounds like a better approach
Mine was already apart but..... read my tag line!
Smart People do Stupid things all the time. I know, I've seen me do'em.

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Fiat G.46 -(restoration in progress, if I have enough life left in me)
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Old 07-11-2016, 04:42 PM
funflying funflying is offline
Join Date: Oct 2006
Location: arvada, co
Posts: 403

A friend of mine, who is an accomplish builder, and a professional in the HVAC world helped me understand some things about pipe threads.
He said the sealant is also a lubricate used to tighten down a fitting where the pipe thread is an interference fit. This allows the installer to tighten the fitting to the proper orientation and will likely feel like "this is too tight and I am going to strip the threads!" He said better to tighten than too loose as it will likely leak.
I also helped with some black pipe gas installation and this guy tried to educate me on these pipe threads. It was pretty much the same story. The pipe sealant was to lubricate the joint and seal, but allow the installer to tighten to where the fitting needed to be so it would line up correctly.

I had a fitting on the brake caliper I could get to seal so I tried a different fitting and tightened beyond my comfort level. Nothing cracked or stripped and no leaks. Use good sealant like Loctite and tighten it well. Consider a different fitting if it continues to leak. Just my experience...good luck!
Patrick Claar
Arvada, CO BJC
RV12, #401, Flying 2013, N612PC
RV6, 1996-2010 sold
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Old 07-11-2016, 08:39 PM
DaveWelch DaveWelch is offline
Join Date: Mar 2005
Location: Huntsville, AL
Posts: 335

Thank-you Scott. All of my leaks were on pipe thread connections that were not tightened enough. I had originally trusted/hoped that the sealant would prevent leaks in a fitting that I was afraid to tighten another full turn. Crank away! I liked the "Medieval" reference, Doug!
RV12 N951DZ
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Old 07-11-2016, 09:15 PM
RFSchaller RFSchaller is offline
Join Date: Oct 2010
Location: Phoenix, AZ
Posts: 2,444

Looking back on tightening my brake fittings I question the torque I applied. I cranked down on them quite a bit which I wonder if it was prudent, but they don't leak!
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Old 11-27-2016, 08:06 PM
AeroDog AeroDog is offline
Join Date: Aug 2011
Location: New London, NC (near Charlotte), Boulder, CO
Posts: 211

Do the leaks occur only at the NPT fitting, or do they sometimes occur at the compression fitting? Approximately how many times can the compression fitting be removed before causing leaks? After reading this thread, I'm considering re-doing all the brake cylinder fittings with Loctite 567 and a bit more torque.


Originally Posted by Dgamble View Post
I used a Permatex thread sealant with PTFE (Teflon) in it. The PTFE provided the lubrication needed to get one more full turn on the fittings into the brake cylinders.
Empennage, fuselage and wing kits complete
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Old 11-28-2016, 07:12 AM
John-G John-G is offline
Join Date: Jan 2012
Location: Northeast Ohio
Posts: 569

Jerre -

I have had four leaks thus far .... three on the brake lines and one fuel.

All of them have been at the threaded NPT fittings.

Three of the leaks were where the fittings screw into the master cylinders for the brakes. I was able to fix two of them by clocking the fitting tighter then removing it and reapplying 567 thread sealant and tightening to the final position. However, one fitting still leaked so I replaced the fitting and used some medium bodied TiteSeal and the issue was resolved. I think the threads on that master cylinder were a little deeper than they should have been.

The other leak was a fuel related leak coming from the NPT threads on the CAV-110 fuel valve screwed into the bottom of the gascolator. This leak took a couple of months to develop. Tightening the valve would not solve the issue. So because it was brass/aluminum coming together, I feared making things any tighter (it was darn tight at this point), so I chose to just replace the CAV-110 valve and here again used TiteSeal. It has been a couple of months now and no leaks yet.

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Old 11-29-2016, 04:50 AM
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Dgamble Dgamble is offline
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Posts: 822

Originally Posted by John-G View Post
So because it was brass/aluminum coming together, I feared making things any tighter (it was darn tight at this point)
Sounds like you successfully avoided repeating my long-ago (my RV-6 era) mistake of applying the JOMT methodology to gascolator work:

"I put the spark plugs back in this evening, and was going to call it a day when I decided to go ahead and put the gascolator back on. I'm been having a problem with the threaded knob that holds it in place being difficult to remove and replace, and today was no different. I got it as tight as I could, but when I turned on the fuel pump to leak test it, I found that it still leaked. This is when I decided to apply the JOMT (Just One More Turn) methodology, and as is usually the case, I went one turn too many. I broke the threaded knob thingy."
Dave Gamble
Grove City, OH

RV-6 N466PG Purchased already flying - SOLD!

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The above web blogs and any links provided thereto are not instructional or advisory in nature. They merely seek to share my experiences in building and flying Van's RV airplanes.
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Old 03-08-2018, 06:06 PM
RandyAB RandyAB is offline
Join Date: May 2016
Location: St Albert, Alberta, Canada
Posts: 389

Installing my AN fittings now. People here are referring to Loctite 567 whereas Van's section 5 suggests Loctite 565. Which is correct? Both perhaps?
Randy P.
1st time builder
RV10 - QB wings and fuse. Working on cabin top
St. Albert, Alberta, Canada
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Old 03-08-2018, 07:35 PM
daveyator daveyator is offline
Join Date: Jan 2011
Location: adelaide, south australia
Posts: 146

AN fittings should not use sealant of any type.On NPT fittings, like the ones in the brake cylinders, I would recommend either permatex#2, or loctite 567. Use sparingly on the tapered thread of the fitting.
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Old 03-08-2018, 08:16 PM
DHeal DHeal is offline
Join Date: Sep 2006
Location: Windsor, California
Posts: 797

MATCO recommends Loctite 567 for their brake fittings. I have had very good success with 567 on all of my RV-12's threaded (oil, gas, brake, etc.) NPT fittings. My local hydraulics supplier had it available in small tubes.
David Heal - Windsor, CA (near Santa Rosa)
EAA #23982 (circa 1965) - EAA Technical Counselor and Flight Advisor; CFI - A&I
RV-12 E-LSA #120496 (SV w/ AP and ADS-B 2020) - N124DH flying since March 2014 - 760+ hours (as of May 2019)!
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