Recently I bled a brake caliper on a (insert make, model, & year here) using a hand-operated vacuum pump. In order to prevent air from seeping past the threads of the bleeder screw, teflon tape was applied to the upper threads–as recommended in other forums.
In a previous life, it was blasphemy to suggest using teflon tape in any system for fear of plugging orifices. What is the recommendation of this forum?
Personally I don't think I would sue the Teflon tap in that use unless it was recommended by the manufacturer. I don't really have any experience with Teflon tape in that use.Air is supposed to leak past the threads of a brake bleed screw. That is why you can bleed the caliper after cracking the screw only a quarter turn or so. The sealing surface is at the tip of the screw.
If someone put teflon tape on the thread of the bleed screws, it was probably to keep moisture out so the screws would not seize. That might be an OK idea in a damp climate.
The concern with Teflon tape is if it is put on carelessly, some pieces could end up in the fluid stream and break off. The loose pieces can lodge in critical parts, like brake pistons, causing bad things to happen. Like Joseph says if it was not recommended, do not use it.
Previous life, such as in the golden age of autos? Personally I don’t see an issue in this use of the tape. The orifice for the bleeders is in the taper at the bottom. Using the tape near the top to seal the threads for bleeding is a great idea. And, I can’t see how any shredded pieces of tape can get into the cylinder or caliper unless the bleeder is completely remove.
A 6 inch piece of rubber hose that is a snug fit on the bleeder nipple is all that is needed to completely bleed the brake system. With the end pointing upward air will be bled. Try it before you disagree. I have tried every piece of equipment that has been on the market for the past 30+ years and none are as fast, none are more efficient.
This is a technique or precaution I am totally unfamilar with.