One of 'Lifes unanswered questions'

Should you use PTFE Tape on the Threads when installing New Brake Pipes

I've not heard of anyone doing it but maybe I'm missing something

Thoughts Guys.....

 

OB, the answer is No. The seal must be between the captive nut on the tube which holds the flare on one side of the join; and the threaded part on the other side of the join. It is the squeezing of the flare between the two threaded parts, not the "watertightness" of the threads, that make the join leak and pressure proof.
Greg

 

NOPE.

Gregs answer plus a few bonus comments.

 

Hi Greg and Grant Cheers!

Another mystery solved

 

I agre with the others.

However, I do put a tiny dab of anti-seize or grease on the threads. Years down the road it might save some poor bloke a bit of aggravation.

Cheers
DD

 

Hi Doug

Cheers! I do exactly the same, as removing OEM Brake Pipes can be a bit of a nightmare, as they often end up unusable or damaged in some way

 

Yup. Tape or sealers only on tapered "pipe" threads. Flared or ferruoe types rely on metal to metal "squeeze".


Caveat, the seats must be "clean" and free of burrs and scratches.


And, use a "flare" wrench, not an open end that messes up the shoulders of the nut.


Some like the ones on my Jaguar's PS must be really tight to avoid seepage.


Carl

 

As others said, the threads are NOT meant to seal. This is evidenced by not being pipe threaded. The flare at the end, male or female, is compressed against the other fitting, the end is whats doing the sealing and the threads are what is being used to force the two together.

I promise you that a good properly flared fitting will seal on its own, but a shitty flare with tape on the threads will absolutely leak.

Another tip to point out, make sure the ends are in-line with each other when tightening. It is sometimes possible to tighten down hydraulic lines offset, the lines will usually center themselves, but its possible to wedge to pieces together offset, allowing a leak.

EXCEPTION: Some fittings use a washer to seal, the ends typically are square, not male or female flare, because there is no reason to be flared.

 

Taper threads require PTFE tape because there is a contiguous leak path, along the bottom of the V of the thread, also to lubricate the thread to allow it to tighten enough. However, I have had a lot more consistent success with thread sealing pastes than with tape.

 

JIC and most other flare fittings should NOT be tightened to much it scores the mating surfaces, torque specs are 30in/lb. I used copper JIC washers when calibrating pressure gauges and nip them up, these would hold 10,000psi all day.

We used these mainly because we were changing fittings often and these prevent scoring of the surfaces.

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