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Brake fluid seeping from master cylinders

 
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dan(at)syz.com
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PostPosted: Sun Aug 06, 2017 5:17 pm    Post subject: Brake fluid seeping from master cylinders Reply with quote

A few weeks ago, I discovered that I had a small brake fluid leak on the left brake of the pilot's side. It was on the upper (low pressure) port of the cylinder, and very small - probably less than a drop a day. I tightened the nut on the hose going to the elbow and that didn't seem to help, so I rotated the elbow another 360 degrees clockwise and that seemed to do the trick (though NPT threads mean I can't just tighten indiscriminately - I have to be careful not to over tighten, though it has to end up pointing upwards).

In any event, I thought the problem was solved, but about a week ago I saw there was still some slight seepage. It hasn't been enough to cause a noticeable drip (at least not yet), but if I run my finger along the bottom lip of the cylinder, it comes away with a bit of brake fluid residue. And I noticed something similar on the copilot's side brakes too just recently, though they seemed dry before. Maybe the higher temperatures of summer caused a few things to resize a bit.

In any case, I'm hesitant to just tighten all the fittings another 360 turn since I don't want to over tighten them and have the master cylinders crack. The seepage isn't when the brakes are used - at least, I can't detect any leaks specifically caused by putting pressure on the pedals. It's just that when the plane sits in the hangar for a few days, I can see residue building up. The current rate of seepage is so small (probably several days for one drop of brake fluid) that I don't really worry about having the reservoir run out between annuals or oil changes (I'm checking it every time I change oil and remove the top cowl and it doesn't seem to noticeably decrease).

Is this something that anyone else has seen? I can live with it by just wiping down the cylinders every week or two. But in the effort to make things perfect, does anyone have any suggestions? I know Van's recommends strongly to not use Teflon tape on the fittings. I'm pretty sure I used Boelube at the time, though that was several years ago. Does its effectivity diminish over time? I can easily remove all the fittings and put more Boelube on the NPT threads if that likely help fix the problem, though the necessity of my having to re-bleed the brake lines after that disassembly gives me pause, especially since I think I used Boelube in the first place so I'm not sure it would help in the long term anyway.

Everything is built exactly according to Van's plans, using the hoses, etc. they provided with the kit. I know lots of people use stainless braided hoses everywhere, but the problem seems to stem from the elbow fitting, not the hoses.

Any suggestions?

Thanks! Dan
---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213


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Tim Olson



Joined: 25 Jan 2007
Posts: 2702

PostPosted: Sun Aug 06, 2017 5:36 pm    Post subject: Brake fluid seeping from master cylinders Reply with quote

Use the liquid teflon sealants...that will do the trick. I think I use loctite 567 but the stuff you can buy at the auto parts store or farm and barn will do just fine.
It's NOT the same as using teflon tape.

Tim

Quote:
On Aug 6, 2017, at 8:16 PM, Dan Charrois <dan(at)syz.com> wrote:



A few weeks ago, I discovered that I had a small brake fluid leak on the left brake of the pilot's side. It was on the upper (low pressure) port of the cylinder, and very small - probably less than a drop a day. I tightened the nut on the hose going to the elbow and that didn't seem to help, so I rotated the elbow another 360 degrees clockwise and that seemed to do the trick (though NPT threads mean I can't just tighten indiscriminately - I have to be careful not to over tighten, though it has to end up pointing upwards).

In any event, I thought the problem was solved, but about a week ago I saw there was still some slight seepage. It hasn't been enough to cause a noticeable drip (at least not yet), but if I run my finger along the bottom lip of the cylinder, it comes away with a bit of brake fluid residue. And I noticed something similar on the copilot's side brakes too just recently, though they seemed dry before. Maybe the higher temperatures of summer caused a few things to resize a bit.

In any case, I'm hesitant to just tighten all the fittings another 360 turn since I don't want to over tighten them and have the master cylinders crack. The seepage isn't when the brakes are used - at least, I can't detect any leaks specifically caused by putting pressure on the pedals. It's just that when the plane sits in the hangar for a few days, I can see residue building up. The current rate of seepage is so small (probably several days for one drop of brake fluid) that I don't really worry about having the reservoir run out between annuals or oil changes (I'm checking it every time I change oil and remove the top cowl and it doesn't seem to noticeably decrease).

Is this something that anyone else has seen? I can live with it by just wiping down the cylinders every week or two. But in the effort to make things perfect, does anyone have any suggestions? I know Van's recommends strongly to not use Teflon tape on the fittings. I'm pretty sure I used Boelube at the time, though that was several years ago. Does its effectivity diminish over time? I can easily remove all the fittings and put more Boelube on the NPT threads if that likely help fix the problem, though the necessity of my having to re-bleed the brake lines after that disassembly gives me pause, especially since I think I used Boelube in the first place so I'm not sure it would help in the long term anyway.

Everything is built exactly according to Van's plans, using the hoses, etc. they provided with the kit. I know lots of people use stainless braided hoses everywhere, but the problem seems to stem from the elbow fitting, not the hoses.

Any suggestions?

Thanks! Dan
---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213







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kearney



Joined: 20 Sep 2008
Posts: 501

PostPosted: Sun Aug 06, 2017 6:47 pm    Post subject: Re: Brake fluid seeping from master cylinders Reply with quote

Hi Dan

I used this with great success.

https://www.amazon.ca/Permatex-80632-Thread-Sealant-PTFE/dp/B000HBNTGY/ref=sr_1_7/136-4197055-7816439?ie=UTF8&qid=1502073596&sr=8-7&keywords=permatex+thread+sealant

I had a similar issue where *apparently* I had a leak on the lower fitting of a cylinder in the starboard side. I did everything I could to fix it. As it turns out the leak was on the reservoir fitting that was spritzing small amounts of fluid onto the fitting. Talk about looking in the wrong place!

Cheers

Les
C-GCWZ flying
C-GROK some assembly required


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Bob Turner



Joined: 03 Jan 2009
Posts: 797
Location: Castro Valley, CA

PostPosted: Sun Aug 06, 2017 8:10 pm    Post subject: Re: Brake fluid seeping from master cylinders Reply with quote

As others said: Boelube is a lubricant. You want a pipe thread sealant. Apply sparingly, not on the first thread. You should have used a thread sealant on all your pipe threads (not teflon tape).

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dan(at)syz.com
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PostPosted: Sun Aug 06, 2017 9:41 pm    Post subject: Brake fluid seeping from master cylinders Reply with quote

Whoops - I misspoke. It wasn't Boelube I used on my pipe threads. I had the name on the brain because I'd recently used it to lubricate the piano hinge pins that go into the cowling.

I can't recall exactly, but I think the stuff I used was EZ Turn Fuel lube (described as a lubricant/sealant).. it's in a tube and *very* gooey and sticky Smile ... not the Boelube that's blue, in a little jar, and oily.

But with that said, it may not be the best product for the job. A thread sealant paste like Loctite 567 or Permatex 80632 as suggested here probably would be better suited. Just so long as it can handle brake fluid properly.

Thanks, everyone!

Dan

Quote:
On 2017-Aug-06, at 10:10 PM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:



As others said: Boelube is a lubricant. You want a pipe thread sealant. Apply sparingly, not on the first thread. You should have used a thread sealant on all your pipe threads (not teflon tape).

--------
Bob Turner
RV-10 QB




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http://forums.matronics.com/viewtopic.php?p=471577#471577










---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213


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bob(at)thelefflers.com
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PostPosted: Mon Aug 07, 2017 1:20 am    Post subject: Brake fluid seeping from master cylinders Reply with quote

Fuel lube is almost as bad. It's not a question of when it will leak, but more like when. It's a ticketing time bomb if you are using it as a thread sealant.


I use a permatex thread sealant and haven't had any issues.


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_____________________________
From: Dan Charrois <dan(at)syz.com (dan(at)syz.com)>
Sent: Monday, August 7, 2017 1:48 AM
Subject: Re: Re: Brake fluid seeping from master cylinders
To: <rv10-list(at)matronics.com (rv10-list(at)matronics.com)>


--> RV10-List message posted by: Dan Charrois <dan(at)syz.com (dan(at)syz.com)>

Whoops - I misspoke. It wasn't Boelube I used on my pipe threads. I had the name on the brain because I'd recently used it to lubricate the piano hinge pins that go into the cowling.

I can't recall exactly, but I think the stuff I used was EZ Turn Fuel lube (described as a lubricant/sealant).. it's in a tube and *very* gooey and sticky Smile ... not the Boelube that's blue, in a little jar, and oily.

But with that said, it may not be the best product for the job. A thread sealant paste like Loctite 567 or Permatex 80632 as suggested here probably would be better suited. Just so long as it can handle brake fluid properly.

Thanks, everyone!

Dan

> On 2017-Aug-06, at 10:10 PM, Bob Turner <bobturner(at)alum.rpi.edu (bobturner(at)alum.rpi.edu)> wrote:
>
> --> RV10-List message posted by: "Bob Turner" <bobturner(at)alum.rpi.edu (bobturner(at)alum.rpi.edu)>
>
> As others said: Boelube is a lubricant. You want a pipe thread sealant. Apply sparingly, not on the first thread. You should have used a thread sealant on all your pipe threads (not teflon tape).
>
> --------
> Bob Turner
> RV-10 QB
>
>
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=471577#471577
>
>
>
>
>
>
>
>
>



---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213


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Albert Gardner



Joined: 10 Jan 2006
Posts: 433
Location: Yuma, AZ

PostPosted: Mon Aug 07, 2017 1:58 am    Post subject: Brake fluid seeping from master cylinders Reply with quote

I started getting air in my lines that I couldn't keep out recently. I'd bleed the brakes but very soon there was some air in the lines. I removed the pilot sides master cylinders and put the copilot ones in their place. Seems to have fixed the problem.

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maca2790



Joined: 26 Jan 2011
Posts: 40
Location: Australia

PostPosted: Tue Aug 08, 2017 12:29 am    Post subject: Brake fluid seeping from master cylinders Reply with quote

I have had trouble with leaks in my Brake lines as well. The Co-Pilots Master Cylinders were leaking from the nipple joints.
I followed the recommended practise of using a torque wrench set to the appropriate torque in conjunction with some Loctite thread sealant.
Either I didn't put enough loctite on or the stuff that I used was old?

I ended up re-installing the nipples on both sides with Permatex 56521. I might add that it also solved the fuel leak problems that
I had with the Fuel pressure Sender and the fuel drain plugs in the wings.

Cheers

John MacCallum
VH-DUU
RV 10 # 41016

--


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TimRVator(at)comcast.net
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PostPosted: Fri Aug 11, 2017 4:56 am    Post subject: Brake fluid seeping from master cylinders Reply with quote

The 2017 update to Van's chapter 5 instructions gives a good treatment
of NPT fitting sealing:
"Because we cannot always fully tighten tapered thread fittings, and
because even after fully tightening the fitting a small spiral leak path
remains along the full length of threads, a thread sealant must be used
during assembly. Sealants appropriate for use on aircraft NPT fittings
areTite-seal, Permatex #2 and Locktite 565. Do not use RTV, Teflon tape
or Fuel Lube on NPT fittings .

When installing the fitting, be sure the threads on both parts are clean
and dry since most sealants will not tolerate any oil contamination.
First determine the clocking position by installing it finger tight and
marking the desired clocking. Remove the fitting and apply a small
amount of sealant to 2 - 3 threads of the male fitting. Leave the first
2 bare to prevent contamination inside the fluid path. Remember, this is
an interference fit so not much sealant is required.

Thread the fitting in with your fingers until you just begin to feel
resistance and then an additional 1.5 - 2 turns. This is general
guidance... you must still use judgement to not over tighten and damage
the threads, but a properly insalled fitting is quite tight. If the
installation requires a specific clocking, when approaching the correct
position you must determine whether you will be able to make another
full rotation and still be within the 1.5 - 2 turns stopping range. You
must avoid turning the fitting backwards in the loosening direction
because it will have a high probability of leaking. If you must do this,
it is best to completely remove the fitting, clean up the threads on
both parts, and try again."

Source: http://vansaircraft.com/pdf/revisions/RV-ALL_05.pdf

--
Tim Lewis -- HEF (Manassas, VA)
A&P
RV-6A N47TD -- 1104 hrs - sold
RV-10 N31TD -- 960 hrs

Dan Charrois wrote on 8/7/2017 1:40 AM:
Quote:


Whoops - I misspoke. It wasn't Boelube I used on my pipe threads. I had the name on the brain because I'd recently used it to lubricate the piano hinge pins that go into the cowling.

I can't recall exactly, but I think the stuff I used was EZ Turn Fuel lube (described as a lubricant/sealant).. it's in a tube and *very* gooey and sticky Smile ... not the Boelube that's blue, in a little jar, and oily.

But with that said, it may not be the best product for the job. A thread sealant paste like Loctite 567 or Permatex 80632 as suggested here probably would be better suited. Just so long as it can handle brake fluid properly.

Thanks, everyone!

Dan

> On 2017-Aug-06, at 10:10 PM, Bob Turner <bobturner(at)alum.rpi.edu> wrote:
>
>
>
> As others said: Boelube is a lubricant. You want a pipe thread sealant. Apply sparingly, not on the first thread. You should have used a thread sealant on all your pipe threads (not teflon tape).
>
> --------
> Bob Turner
> RV-10 QB
>
>
> Read this topic online here:
>
> http://forums.matronics.com/viewtopic.php?p=471577#471577
>
---
Dan Charrois
President, Syzygy Research & Technology
Phone: 780-961-2213


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