I'm having a heck of a time with leaky master brake cylinder fittings. I'm going to try loctite 567. Is there a cure time before putting brake fluid back in?
Yep, 567 is good stuff. It does take a few days to fully set up but usually it will seal fine even when still "wet". But I didn't use any on my airplane.
For brake fittings that are pipe thread I use Loctite 545 Hydraulic sealant.
This stuff is better for the smaller "finer" threads. It cures pretty fast.
According to the following directions. Loctite 567 needs to cure for at least 24 hours to reach full strength. It does have immediate sealing strength. But to be safe it sounds like 24 hours would be best.
567 is an anaerobic adhesive. The stuff you see around the threads after assembly will never cure fully, because it's exposed to air. The stuff in the joint will cure quickly. Full strength comes after 24 hours, but well before that you'll find that if you try to disassemble the joint it will come apart far more grudgingly than it went together. I use 567 all the time in the hydraulic assemblies I put together at the place that supplies me with the money that I need to keep my RV-7 airborne. It works very well- our environment is 5000 psi and a shake table with 21g acceleration.
I too used 567, had leaks. Mostly caused by not tight enough fittings. I ended up turning the two fittings in one more rotation and that sealed them up. Fingers crossed, because it ain't no fun head first diving in the front of an 8 to fix leaking brake fittings!
For most of my life I've had excellent results using Rectorseal #5 on all pipe threads. Matco however specifies Loctite 567 to seal threaded fittings to their brake systems, so that's what we now use and have experienced excellent results. Just an example that excellent results can be obtained with many brands of thread sealant provided both male and female threads are clean and the parts are torqued to proper values. YMMV
The taper pipe thread is governed by:
MS 22677 - Fitting End, Taper Pipe Thread, Standard Dimension For
And
MIL-P-7105B - Pipe Threads, Taper, Aeronautical National Form, Symbol ANPT, General Requirements For
The thread form tolerances result in a truncation between the crest of the male thread and the root of the female thread. I believe the primary leak path is the spiral at the crest and root of the thread. The secondary leak path is at the mating flanks of the male and female threads.
There will always be a tolerance accumulation somewhere in the threads that forms a leak path, even when the fittings are properly tightened. So always use a sealant.
, that worked....
