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Old 11-08-2017, 06:37 PM
bob888 bob888 is offline
Join Date: Jul 2012
Location: Fresno, CA
Posts: 213
Default Brake fluid leaking

There is a persistent, minimal drip of brake fluid off the bottom of my left brake master on the left rudder pedal. I can't detect any fluid from any point above the lower attachment bolt and specifically no leaking around the NPT threads where the brake lines attach. The only thing I can think of is a crack in the very bottom of the master cylinder. Anyone have ideas on this?
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Old 11-08-2017, 08:30 PM
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9GT 9GT is offline
Join Date: Jan 2010
Location: Southern Michigan
Posts: 1,558

One of my masters on my RV-10 leaked from day one after I filled and bled the system. I thought it was leaking from the fittings also. After fooling with the fittings for a couple weeks on and off, I finally crawled in and removed the cylinder. After disassembly of the cylinder, I found a piece of metal shaving inside from the machining process and the steel piston rod that comes out had a pretty deep gouge in it. I polished it out with the deburring wheel, cleaned it all up and replaced the O-ring seals. Problem solved. I was not happy with the quality control but they are reasonably priced and that's the only one I ever had problems with.
David C.
Howell, MI

RV-9A: Under Construction.
RV-10: Completed 12/29/2013 SOLD 08/23/2016

"Donor Exempt" but donated through Dec. 2019
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Old 11-09-2017, 12:30 AM
erich weaver's Avatar
erich weaver erich weaver is offline
Join Date: Aug 2006
Location: santa barbara, CA
Posts: 1,586

Pretty common to have leakage after some years of use. There are inexpensive rebuild kits available from the brake manufactures, ACS, and Vans. Pretty easy once u get the master cylinders removed. Worked for me.

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Old 11-09-2017, 06:25 AM
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Bill.Peyton Bill.Peyton is offline
Join Date: Sep 2009
Location: St. Louis, MO
Posts: 1,662

I too had a persistent leak that was difficult to cure and to find. It ended up the lower NPT fitting that was leaking. After several attempts to cure it I finally had to go to a steel fitting and I used a Loctite 567 pipe thread sealant. Hasn't leaked in 5 years.
Bill Peyton
RV-10 - 890
First Flight Oct 2012
Aviation Partners, LLC

Last edited by Bill.Peyton : 11-10-2017 at 06:11 AM.
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Old 11-09-2017, 12:08 PM
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Paddy Paddy is offline
Join Date: Jul 2008
Location: Chicago
Posts: 234
Default Loctite 567

I too had a persistent leak from the lower fittings on my master cylinders. Tried all the usual sealing compounds - Permatex #1 and #2, Bakerseal etc and nothing worked. Eventually, someone recommended Loctite 567. This stuff has both PTFE, which provides some lubrication so you can get another turn on the fitting, plus an anaerobic adhesive component that sets up overnight. I also went with steel fittings on the bottom like Bill did. No leaks in the last 100 hrs
Flying as of 10/30/16 after 8 yrs building
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Old 11-14-2017, 10:07 AM
rdrcrmatt rdrcrmatt is offline
Join Date: Oct 2014
Location: Milwaukee, WI
Posts: 180

Ours started leaking right after we got the plane and within a week the right seat right pedal went dead. Left seat pedal is fine still.

Really frustrating as they were brand new as well.

I haven't yet gotten the supplies, or figured out how to fill / bleed the brakes so I haven't gone after the issue.
2018 Dues Paid.
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