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Sealing Threaded Connections

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Hi Dave,

Permatex pneumatic and hydraulic sealant is designed for making high pressure hydraulic and brake line connections. It prevents thread leakage (which should not be a problem with a good connection), but also protects the threaded connection from corrosion. You will appreciate that if the fitting ever needs to be opened. A very light coating on the flared connection will also help seal small surface imperfections.

"54540 Product Description
Permatex High Performance Thread Sealant is designed for locking and sealing high pressure hydraulic and pneumatic systems. This thread sealant does not contain harmful fillers or particles that could contaminate system fluids, foul valves, or clog fine filters and screens. Reliably cures on ā€œas receivedā€ fasteners and controlled locking strength affords easy disassembly.

Formulated specifically for sealing tapered metal pipe fittings

Cures rapidly to withstand up to 10,000 PSI

Prevents galling and protects mated threaded areas from rust and corrosion

Prevents leakage from vibration, temperature cycling and extreme pressures

Allows parts repositioning after application"

Regards, Bill

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I'm with Bob on this one; the threads shouldn't need sealing and if they do, you should revisit your flared ends. I have, however, taken to applying a little bit of anti-seize--preferably the high-temp variety--on the threads to help in removal (but not on the first thread or two). I gave it a lot of thought and decided as long as you don't overdo it contamination of the fluid shouldn't be an issue; again, if your flare is sealing properly.
 
I agree with the above.
Old flares are prone to cracking and not seating centered.
Old tube nuts can also crack and distort.
No sealer is needed.
 
Hi Dave,

I decided to add the following information because there was an implication that using thread sealer on hydraulic fittings was possibly an incorrect procedure. It is not. And, no one said it was meant to fix a bad flare or leaking fitting.

In fact, a good hydraulic thread sealer often prevents a poor seal during brake (or other hydraulic fitting) makeup by acting as a lubricant so (i) the flare (or female fitting) easily fits over the tapered male fitting and (ii) gently conforms to the fitting with reduced pressure. As with any fitting, the force/pressure required for good makeup is to overcome friction and then ensure improved conformance (yes, the flare or female fitting does require some pressure to conform to the male fitting).

As mentioned before, the thread sealer also:

1 Prevents galling and protects mated threaded areas from rust and corrosion by preventing air or water from entering the fitting.

2 Prevents the fitting from loosening due to vibration, temperature cycling and extreme pressures.

3 Allows for parts repositioning after application. This is extremely important during makeup.

4 Reduces the total force/pressure needed for good fitting makeup.

5 Allows the fittings to be easily separated in the future.

Proper brake fitting makeup usually requires a series of smooth "tightening steps":

1 Align the pipe/fitting for makeup

2 Initially tighten the brake fitting gently as the parts come together.

3 Then, tighten the fitting slightly more as the parts begin to conform.

4 Slightly back off the fitting, and then re-tighten it a few degrees of additional rotation.

5 Due step 3 several times until you feel good makeup conformance. Yes you can feel it because the parts are lubricated and there is less force required for makeup.

6 Finally, snug up the fitting for service. If done correctly, it requires little force and it will not leak or fail during service.

I design, build and install equipment that uses hydraulic lines/fittings in extreme environments (corrosive environments with high temperature and high pressure). We have never lost equipment due to a hydraulic seal failure.

Regards, Bill

EDIT1:

Might as well add this also:

Conventional brake fluids (which are corrosive) can cause steel fittings to crack. This is also one (of several) reason the best car manufacturers use Copper-Nickel brake lines and brass fittings. A properly sealed brake fitting should not crack and it should be easily removable.

EDIT2:

Only a thin film of sealant is needed to prepare the fitting. A thin film will seal the threads correctly and lubricate the parts. I add this before anyone starts complaining about dipping the parts in the sealant and having it dripping off the fittings during makeup. :-(
 
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My issue with this product--and I'm generally a fan of Permatex products-- is that if it is an effective sealant and if any fluid is getting past the flare connection you won't be able to spot it. I think, at least for automotive application 'thread dressing' would be a better name for it (their site says for 'brake fittings,' but it's not a raging endorsement). Given our brake lines and fittings are steel and cylinders are usually aluminium dissimilar metals corrosion will gunk up the threads over time; hence why I use a little anti-seize (it's not a sealant; it won't hide the evidence of a failed connection).

Cupronickel brake lines are excellent; I bought a full set from Automec for my BJ8 and have been replacing the steel a piece at a time.

sealĀ·ant
/Ėˆsēlənt/


noun
noun: sealant; plural noun: sealants
  1. material used for sealing something so as to make it airtight or watertight. [i.e. to prevent or stop leaks--my words]
 
Im with Bob . The tiniest amount of anti-seize due to dissimilar metals is more than enough . Flare /hydraulic fittingā€™s donā€™t need sealants . If they do you either have bad fittings and or sealing surfaces due to age corrosion/damage and or poor or incorrect flaring tools/techniques .
Either way weā€™re talking about brakes here where safety and reliability are P1 .
 
This is an interesting discussion. When I took vocational auto mechanics class in 1968 our instructor adamantly refused to allow any sealant to be used on flare fittings. He insisted on metal-to-metal seals because sealants can fail. This was at a time went our cars were still on the road as daily drivers and serviced by ordinary repair shops and we were being taught current 'best practices' so we would be prepared for jobs in shops.

If you read the instructions on the Permatex 54540 shown above it says: "Formulated specifically for sealing tapered metal pipe fittings" but makes no mention of using it on flare fittings.

I realize there have been huge changes/improvements in the world of sealants since the late '60s and a lot of sealants are vastly superior to what was available then and that many applications may have different requirements/recommendations but in scouring the internet, I find universally (including the new AI) that no one recommends sealant on brake flare fittings.

I agree with corrosion protection of threads, but I think I will continue do flare fittings 'dry'.
 
The last major brake line work was on my BN2 a few years ago. Using mild steel brake lines--I'd been given a large roll of it--I was having a hard time making flares; the ones I made were either distorted in shape and/or had tiny cracks at the flare (I attributed this to the hardness/brittleness of the steel). I eventually came across a video by a shadetree mechanic who had a solution: anneal the end of the line. Heat the last half-inch of the line to 'cherry red'--a propane torch will suffice--and let it slowly cool in air (i.e. don't quench). After doing this I was able to make flares that were perfectly shaped, with no cracking and which sealed perfectly. I was concerned that the annealing process would weaken the flare, and it probably does somewhat, but decided that even annealed steel would be sufficiently strong (though I have no 'data'). Annealing the end of the lines allowed easier formation of the flares, which I believe is one of the advantages of cupronickel lines, which appear to be somewhat softer than steel and hence are more easily formed.

I was trying to get some really tight bends where the line fits into the rear wheel cylinders--the common tube-bending tools will only make larger bends--and ending up using a cheap tool from HF. Like most of these tools they will leave a small crease at the end of the bending channels. This concerns me, but I decided to live with it.


On another note, since the rear lines, from the 'T' on the axle to the wheel cylinders, on a Big Healey are rigid, and the wheel cylinders should slide back-and-forth for the 'self-energizing' effect these lines could conceivably work harden over time (though I've not heard of any issues).

And, I've found the threads on steel fittings and aluminium cylinders aren't conducive to smooth-and-easy torquing. Anti-seize is a lousy lubricant, but it helps here and for eventual removal.

Anybody else lay awake at night thinking about this stuff?
 
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