bleed screw -- teflon tape

[Coyote]

Anyone ever use teflon tape on a bleed screw? I'm fixin to swap out the seeping bleed screw for another. Just wonder if the sealing tape is a good (or bad) idea.

[Vintageman]

What bleed screw? Carb bowl. I think fresh OEM washer should work best?

There is the "Yellow" teflon tape version that holds up better to petroleum... intened for natural gas type applications... think i have seen in home depot for example

[Coyote]

brake caliper

[Cliff]

Tape won't work on brake bleeder. Try another bleeder screw.

[Coyote]

That's the plan Cliff. I have another to trade out. I tried to do that today thinking not much fluid would come out as it wasn't under pressure. I cracked the bleeder and fluid started flowing everywhere. Then I thought about using a hose and a catch container. But then I figured no matter how I route the drain hose, the fluid would still be way above the caliper. Then I realized I am going to have to purge the whole system to change the silly bleed screw. I walked away and mentally put it off. I'll HAVE to do it, but not today

[pearljam724]

It's not a good idea to use Teflon tape around gas or brake fluid. Those liquids will turn it into a goo. With possibilities of clogging. I tried it once on the threads of petcock bowl and the internals were a mess when I opened it back up. I know a lot of bleeders today are manufactured with a similar thread sealant that is brushed on as a liquid and dries hard. Speed bleeders for example. Don't know what that sealant is called, who makes it or even if it's available to the public ? I would tap a new thread and use a larger bleeder. Your caliper threads are worn. Nothing else will likely fix it, but tapping a larger size.

[akendall1966]

They normally seal on the cone tip so the threads play no part in the seal other than to drive the cone inot the seat. Changing the bleed screw may have no effect if it is damage or debris on the caliper surface the cones of the screw seats into.

[pearljam724]

[quote="akendall1966"]They normally seal on the cone tip so the threads play no part in the seal other than to drive the cone inot the seat. Changing the bleed screw may have no effect if it is damage or debris on the caliper surface the cones of the screw seats into.[/quote

The bevel you speak of will not seal if the threads are worn. It has everything to do with the threads. Without good threads. The bevel will not seal. A larger bleeder will seal at the bevel just the same as a the original as long as the threads are applying enough pressure. Debris could also be a problem from the worn threads.

[akendall1966]

The OP was asking about teflon tape helping to seal the nipple. But as I think we are agreeing the seal is made by the cone and not the threads. So my point was adding tape has no effect on the sealing of the bleed screw, as this is after the seal and fluid would still leak out of the centre hole via the cross drilled hole on the unthreaded portion above the cone. Assuming it like the part below



But, sure you need reasonable threads to apply pressure and drive the cone into the seat with reasonable concentricity and perpendicularity.

[Coyote]

My question is how could you possibly wear out the threads? It's something you rarely address, and even at that, less than half a turn is all the movement you need.
For some reason the cone is not sealing. What is strange is you would think the fluid would seep out the center hole, but this one appears to be seeping around the threads. But it has to be the cone, otherwise it wouldn't seep at all

[pearljam724]

Someone or multiple people before you over torqued the bleeder one too many times. Like you said, under normal circumstances the bleeder should seal with minimal torque. Majority of the time you can see the bleeder wiggle a tad if you try to wiggle it when the threads are shot. You would be surprised how many people over torque them thinking it will seal better. I've bought brand new wheel cylinders for cars, when manufactured the threads were tapped poorly and the bleeder wiggled too much not creating a good seal straight out of the box. The cone needs pressure created from the threads. It will bypass the cone, followed by threads when the threads are too worn.

[akendall1966]

My question is how could you possibly wear out the threads? It's something you rarely address, and even at that, less than half a turn is all the movement you need.
For some reason the cone is not sealing. What is strange is you would think the fluid would seep out the center hole, but this one appears to be seeping around the threads. But it has to be the cone, otherwise it wouldn't seep at all

Speculation from far away, capillary action draws it up the thread but leak is small and not enough to feed this action and fill up the centre bore?

[Coyote]

Purged the system, changed out the bleed screw and bled it again. So far - so good.