That is a "Speed bleeder" in the photo. They put sealant on the threads so that it doesn't suck in air if you use the pump-the-lever method to bleed your brakes. Most people use a constant vacuum or a pressure bleeder when using regular bleed screws and sealant is not needed to prevent air from returning into the system. Some have used sealants or Teflon tape successfully to seal just the threads for bleeding but I've seen a few times where the sealant got sucked into the system causing blocked passages..... not good.
The bleeder you pictured looks like a speed bleeder to me. The bottom of the bleeder (tapered seat) is what does the sealing, nothing to do with any threads, unless stated above, you need to pull a vacuum on it or it's a speed bleeder (which will need the threads sealed (from air leakage!) to operate it properly and draw the more viscous brake fluid into the the master when you release the lever, other wise you're just going to pull air back into the caliper.
The ones for cars (not speed bleeders) Also have thread sealant. I'm not suggesting not to investigate and replace but as a extra insurance. I suggest you look harder at the above picture. It even mentions a patented thread sealing system
You're not real bright mechanically are you? Again...and S l o w l y.... It doesn't Seal Brake Pressure on the FuckingThreads... Depending on sealer, on a brake bleeder that May have a damaged seat is a Bad Idea.. and may cause bodily harm.
Don't know of any brake system that relies on thread seal to make a seal, everything is flared, just like the bleeder tip, only exception is banjo connections. I don't get the confusion? Never seen a car brake have sealers on the threads. If there is on some exotic shit, its probably to keep shit OUT of the threads, not keep brake fluid in. But, i haven't seen it on any of the american junk we work on in the last 20 years.
It is there to aid in bleeding the system. Back when we had stone and wooden wheels we used grease on the threads to prevent air from messing with the bleeding process.
So I cleaned the top of the threads well and let it sit. No fluid. Then I used a zip tie to hold the lever overnight. Tiny amount fluid around threads. This tells me the seat isn't sealing properly. It's as tight as I'm willing to tighten it. So Triumph doesnt list just the bleed screw separately. Looks like I can buy these just about anywhere. The stock one is aluminum. Do i need to replace it with an aluminum one or would steel, stainless steel work? Is there a company that makes quality parts. Last thing I want to do is replace this with Chinese junk.
My only concern would be galvanic corrosion at that point, but it should work if you can't find a suitable aluminum one. Are you 100% the bleeder is aluminum or is it just not ferrous?
Personally, I'd swap them out for Steel/Stainless and never give it another thought. (Not a fan of alum bleeders or bolts).
If the fluid is able to work its way past the sealing surfaces and wick along the threads, how much fluid is coming out of the bleed hole? It seems to me that fluid always finds the path of least resistance, so why would the fluid choose to work through the threads instead of just leaking out of the big open bleed hole at the end of the bleed nipple?
I suggest you look harder at the above picture. Did you read what they specifically say the patented thread sealing system is sealing out? Based on your input here and in some other threads I haven't decided yet if you're a troll or just stupid.
You'd think. Maybe just residual fluid hanging around. If the port to the outside is full of fluid it will eventually try to level itself out and leak around the threads to do so. I always just blow mine out with compressed air really well, then I know if anything comes back it's a leak.