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Hardware help (Brake Master Cylinder Reservoir)

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Maxrate

Well Known Member
So I'm helping a friend on his condition inspection and his brake MC reservoir has come loose over time. Were looking for a fitting that will allow the reservoir to be tightened with the MC and stay aligned. The original builder just TIG welded the thing on. Both are 3/8 pipe thread. I searched the spruce catalog and couldn't find a good option. Just trying to help a friend...

2qjkihi.jpg
 
You could tear down the master and cut the threads a little deeper. Good opportunity to replace the seals while you are in there.
 
Possible fix.

Take it apart, clean and reassemble with green locktite???

The green stuff will stop a weeping rivet in a fuel tank, hopefully will work with brake fluid.
 
Thanks Mike. That’s a thought. The problem is the placement of the rudder pedal in the cockpit. If someone gets in and bumps the MC it is prone to rotate. Really a poor design. I did find this fitting. But think it may rotate too. I could also disassemble, clean and reassemble the MC and reservoir with red locktite 262 permanent. It will be slightly loose when assembled until the locktite sets up. Any ideas appreciated.

https://thornwellwarehouse.com/prod...NPT-Male-to-NPT-Swivel-Female/478-dash-140466
 
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Teflon tape on the threads will likely fix this issue.
Even though some say Teflon tape should not be used, there is no rule against its use. Just make sure the tape is only on the threads and not blocking the hole.
 
So I'm helping a friend on his condition inspection and his brake MC reservoir has come loose over time. Were looking for a fitting that will allow the reservoir to be tightened with the MC and stay aligned. The original builder just TIG welded the thing on. Both are 3/8 pipe thread. I searched the spruce catalog and couldn't find a good option. Just trying to help a friend...

2qjkihi.jpg

You said 3/8, but I think it's more like 1/8 pipe thread. No need for a jam nut on pipe thread, just a sealant like Teflon paste and retighten it up!
 
1/8? correct Tom. My problem is the geometry. Here is a pic. When the reservoir is tight it?s almost at a 90* angle. I?ve tried wrapping Teflon tape but if you bump it it moves. This ones got me stumped. I like the idea of locktite and a jamnut but am concerned about the seal. :confused:

x6cr5.jpg
 
1/8? correct Tom. My problem is the geometry. Here is a pic. When the reservoir is tight it?s almost at a 90* angle. I?ve tried wrapping Teflon tape but if you bump it it moves. This ones got me stumped. I like the idea of locktite and a jamnut but am concerned about the seal. :confused:

x6cr5.jpg

As mentioned, a jam nut does not work with NPT. It will not seal well; It is a tapered thread and you must force it in if you want it to seal. If you can turn it by bumping it, it is WAY loose. NPT threads get tightened with much greater force than your typical AN3 bolt.

Larry
 
I have found that Loctite 567 sealant not only seals well but makes it very hard to remove once cured (24 hrs). Thread lockers like the red, are the similar anaerobic materials, but with higher strength. Green as better wicking and medium strength, not likely what you want. Access the hot link.

I think I would try the standard 567, rotate to the correct position 3/4 past where you show, let it sit for 24 hrs to yield full strength, and then decide. Test with some known torque and if it does not move, then install. The 567 has some teflon so it is unlikely to gall. Just an opinion.

It seems the only other simple choice would be high strength epoxy, but the Loctite might just have better shear strength anyway. The Loctite TDS does not give shear strength, but a breakaway torque several times higher than installation torque.
 
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