TR2/3/3A Odd observation when bleeding

[TRclassic3]

Due to a caliper leaking I pulled and rebuilt the calipers (A type). When attempting to bleed kept getting lots of small bubbles from the same caliper that had originally been leaking. Using DOT 4 fluid. Went through some gyrations to determine if it was really leaking or just the result of messy bleeding. Have determined that it is leaking from same cylinder as original leak. But here is the odd thing: The brake can be pumped and held with no leak evident. Crack the bleeder and fluid drips off the bottom. Definitely not coming from bleeder or piping but from cylinder. Obviously have to redo that cylinder, but wondering if anyone has an explanation for the behavior.
Thanks

 

[RGK]

Probably coming from the bleeder threads, they may be worn. Speedbleeder dot com sells thread sealant.

 

[TRclassic3]

Probably coming from the bleeder threads, they may be worn. Speedbleeder dot com sells thread sealant.

Thanks. I initially thought that was a logical source but wrapping a towel around as I opened the bleeder eliminated it.

 

[CJD]

Opening the bleeder no more than 1/4 to 1/2 turn prevents the back flow of air through the threads.

 

[charleyf]

This may not be your problem but I just experienced a what I thought was a leak on a front caliper. I would find fluid around the base of the hose. I guessed it was the copper washer. But after about four corrections, I finally determined that the fluid I was finding came from the fluid left in the bleed screw after bleeding. After I cleaned everything up, that remaining fluid would slowly ooze out and down to the base of the hose over night.
Charley

 

[DavidApp]

I have been wrapping the bleed screw threads in PTFE tape. That seems to stop the tiny bubbles when vacuum bleeding.

David