Air Leaking Through Brake Bleeder Valve Threads

[Guest]

I was bleeding my lines with my little handpump and was pulling in air. In the rear it wasn't even able to pull any fluid. After some head-scratching I saw that there looks like there should be something between the bleeder valve and the caliper housing itself (perhaps a gasket or O-ring?) but on all 3 bleeders there is nothing. To feed my curiosity I put some grease around the bleeder valve and noticed a huge improvement.

I looked online for photos or diagrams and I don't see anything that is supposed to seal up those threads though. Am I missing something? The bleeders are getting replaced but is seems to me just the threads on the bleeder are probably not designed to be airtight themselves.

As always, I appreciate any input.

[Agemax]

wrap some teflon thread tape around the threads, i do that do all my bleeders.
guarantee no air leaks

[G.S.Joe]

That was a consideration, but I was concerned that I was just putting a band-aid on instead of replacing a missing gasket. Also I wasn't sure how the PTFE would react with brake fluid.

[GateKeeper]

nothing missing, just the bleeder nipple, and the brake caliper, as mentioned use the teflon tape, or pipe dope, etc....

do the threads look mangled, did someone cross thread them at one point ?

if they are clean and sharp then there is no worry and just use the above to solve the leak

.

[Crankthat]

I have never had a problem with mine but the Teflon tape sounds like a reasonable solution.
Think I would replace bleeders first though as the problem would be more likely on the bleeder threads and would not want to risk damaging the softer metal of the brake assembly with bad bleeder threads.
I am curious now though as to if anyone has drilled and tapped or re tapped a brake assembly before and what for results?

[Agemax]

i have always used teflon tape there, even with new bleed nipples and good threads in the calipers. it just guarantees a good seal.
it works perfectly well with brake fluid.
it is Not just a quick fix, some bleed nipples come with it already on from new!

[Sadsak]

Keep in mind that the threads on a brake bleeder were never intended to be air tight. The seal for the brake bleeder to the caliper is the tapered end of the bleeder sealing to the tapered seat in the caliper body. If you are trying to vacuum bleed your brakes then a wrap of teflon tape on the bleeder threads will work. Do not drill or tap the bleeder hole in the caliper as that will destroy the tapered seat.

[chuck hahn]

I was gonna suggest you run a Qtip down the bleeder nipple hole in the caliper to wipe the bottom out well..and inspect them end of the bleeder itself for pitting or other wear damage.

[Nessism]

Keep in mind that the threads on a brake bleeder were never intended to be air tight. The seal for the brake bleeder to the caliper is the tapered end of the bleeder sealing to the tapered seat in the caliper body. If you are trying to vacuum bleed your brakes then a wrap of teflon tape on the bleeder threads will work. Do not drill or tap the bleeder hole in the caliper as that will destroy the tapered seat.

Gold star for sadsak.

Teflon tape helps, but you can still get leakage. I just ignore the bubbles when power bleeding.

[G.S.Joe]

Thanks for the suggestions. The bleeders didn't look X-threaded but they were rusty and had a lot of play once they were open. Sounds like I just need to replace them and clean the bore in the caliper. If that fails I'll use the teflon tape.

[Maddevill]

I found that if you only loosen the bleeder a bit then it won't suck as much air. if you really loosen it to bleed then is when the air sucking problem exists.