What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Brake fluid leaking

bob888

Well Known Member
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?
 
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.
 
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.

Erich
 
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.
 
Last edited:
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 :)
 
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.
 
Back
Top