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  #1  
Old 06-12-2016, 05:10 PM
n74846 n74846 is offline
 
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Location: Boca Raton, FL BCT
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Default Pipe Thread Sealant

I have a couple of weeping brake fluid points on my master brake cylinders mounted on the pedals. Before I start the project I want to confirm that Teflon tape is the acceptable thread sealant to use with brake fluid. (I have already tried tightening the fittings with little improvement.)

Thanks for your input!
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  #2  
Old 06-12-2016, 05:21 PM
daveyator daveyator is offline
 
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Location: adelaide, south australia
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Teflon tape is not recommended. A paste type sealant is what you want. Now to start a 'primer war', I'd suggest either Loctite 567 pipe sealant, or Permatex #2.
I assume the leaks are from the NPT threads in the actual master cylinder. The line fittings, if correctly assembled, should not require sealant, and should not leak.
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Last edited by daveyator : 06-12-2016 at 05:41 PM. Reason: Further information
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  #3  
Old 06-12-2016, 05:24 PM
Nova RV Nova RV is offline
 
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Technically, Teflon tape is considered a thread lubricant which allows the threads to be tightened further than without. It is not a sealant.
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  #4  
Old 06-12-2016, 06:08 PM
aerhed aerhed is offline
 
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I only will use ACME 4 part epoxy primer, and...uh, oh wrong thread.
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  #5  
Old 06-12-2016, 07:47 PM
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bullojm1 bullojm1 is offline
 
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+1 for using Loctite 567. I had a leak in the same place and 567 fixed it nicely. Since I needed to drain all the brake fluid from my system to reseal the NPT fittings at the master cylinders, I also resealed the fittings at the calipers since they were also slightly leaking.
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  #6  
Old 06-12-2016, 08:12 PM
alpinelakespilot2000 alpinelakespilot2000 is offline
 
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Quote:
Originally Posted by n74846 View Post
Before I start the project I want to confirm that Teflon tape is the acceptable thread sealant to use with brake fluid.
Thanks for your input!
Teflon tape is generally regarded to be off limits on aircraft, though I'm sure many get away with using it. And, in fact, my pitot line fittings came with some on the threads. Still, there's always a chance a bit of tape can get in the system and there are other alternatives that don't have the same downside. As others mentioned Loctite 567 or the Permatex equivalent, is a good choice, as is TiteSeal. I initially used fuel lube (EZ Turn) per Van's plans with good results, but others have had problems with that leaking. Now I just use the Permatex equivalent of 567.
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Last edited by alpinelakespilot2000 : 06-12-2016 at 08:19 PM.
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  #7  
Old 06-12-2016, 10:41 PM
n74846 n74846 is offline
 
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Thanks to all for the input. I will stay away from the Teflon and stick with one of the recommendations.
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  #8  
Old 06-13-2016, 06:17 AM
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Dgamble Dgamble is offline
 
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Quote:
Originally Posted by n74846 View Post
Thanks to all for the input. I will stay away from the Teflon and stick with one of the recommendations.
I used a Permatex thread sealant with PTFE (Teflon) in it. The PTFE provided the lubrication needed to get one more full turn on the fittings into the brake cylinders.

https://www.zoro.com/permatex-thread...Q&gclsrc=aw.ds
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  #9  
Old 07-10-2016, 10:37 AM
DaveWelch DaveWelch is offline
 
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Location: Huntsville, AL
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I used the Permatex #2 when assembling the brakes a couple of years ago. Last week at inspection the DAR noticed that every one of the Master Cylinder NPT fittings was leaking. Note that the brakes have had virtually no use since assembly. I'm in the process of disassembly, cleaning, and reassembly with Loctite 567 this time.
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  #10  
Old 07-10-2016, 10:49 AM
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DonFromTX DonFromTX is offline
 
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I use 567 on everything and have been happy with it. That said, I had several leaks in my brake lines as well. Even though carefully tightened with my expertly calibrated right arm, they leaked - even without actual pressurized use!. I took them all loose and did it over with more tightening force (and more 567) and now they are not leaking. There seems to be some slight mismatch on the threads of the fittings or the master cylinders, as well as some other places in the brake lines, and what I would call "over tightening" seems to solve the problem.
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