Teflon tape on bleeder screws?

ST-Traveler

ST-Traveler

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2007 ST1300
I have read several articles about possible air bubbles coming through the bleeder screw threads during the normal brake bleed process.
I have also seen and read several different places to prevent this phenomenon to add "Teflon" tape to the threads.
Question is:
1. can the screw be removed at any time and tape added without introducing air into the system?
2. has anyone actually done this or is there something else more effective ?
3. does this work?

Thanks in advance
 
I taped them carefully on more than one bike and never had to reapply tape ever again. Use good technique and leave no possibility the tape will ever block the passage then forget about them. Practically speaking when bleeding is done the threads are at “the end of the line” and if under suction air never enters the circuit upstream of the bleeder.
 
dduelin said:
I taped them carefully on more than one bike and never had to reapply tape ever again. Use good technique and leave no possibility the tape will ever block the passage then forget about them. Practically speaking when bleeding is done the threads are at “the end of the line” and if under suction air never enters the circuit upstream of the bleeder.
Click to expand...
Get Speedbleeders to make the job easier..
 
CollingsBob said:
Get Speedbleeders to make the job easier..
Click to expand...
I used Speedbleeders on my ST for brakes and clutch. A little more expensive overall than a MotionPro bleeder., but makes the bleeding process dead simple.

Speedbleeder sells a paste to reapply to bleeder threads to seal out leaks if this becomes an issue. Never needed it.

https://www.speedbleeder.com/install.htm
 
ST-Traveler said:
1. can the screw be removed at any time and tape added without introducing air into the system?
2. has anyone actually done this or is there something else more effective ?
3. does this work?
Click to expand...
Speedbleeders also sells a pipe dope you can apply to the threads of any bleeder. Their bleeders come with pipe dope on the bleeder. Practically speaking, any pipe dope that is brake fluid (mineral oil based, with whatever additives (IDK)) resistant should work.

To answer your questions:
1. Maybe. If you remove the bleeder to tape/dope it, fluid will normally flow out and be replaced by fluid coming from the master cylinder. If you jostle the wheel and move the caliper, the pads and pistons might move sucking air into the caliper. Best to do this just before bleeding the brakes.
2. I swapped my bleeders for speed bleeders w/ their pipe dope on my V Strom. At $8 per, it was going to cost real money for my ST1300.
3. yes, but over time you can wear, displace the teflon tape or pipe dope and might have to do it again.

Consider that a few kazillion bleeders have been loosened without tape or dope by mechanics around the world who ignorantly successfully bled their brakes. What I am saying is neither tape or dope is necessary, proper procedure is.
 
After a while, Speedbleeders' threads wear and the lose the efficacy for which they were intended. A much better solution is made by a lesser know brand called Stahlbus (German). Similar in principle to Speedbleeder except they use a base that stays tightened to the MC/Caliper and virtually eliminates thread wear. The bleeder section is that which is loosened to bleed than tightened afterwards. A bit more expensive, but by far the best product, both quality and functionality, I've seen and used (decades of experience on most makes), and what I use almost exclusively.

The stahlbus® bleeder valve

www.stahlbus.com www.stahlbus.com
 
The issue only arises when using vacuum pumps. This sucks fluid out of the system rather than pushing it out with brake lever pressure. But when you undo the bleeder valve, the cone at the end that forms the seal is no longer in contact and no thread is airtight - so air is sucked past the threads from the outside and in through the hole in the side of the bleeder valve which is at ,the bottom of the threads and above the pointed cone at the end.

So no air enters the brake lines in this situation, you just cannot tell whether you are getting any more air out because of the stream of tiny air bubbles being sucked past the threads from outside.

Teflon tape helps with this, but it doesn't completely eliminate it.

The Honda manual suggests adding teflon tape to the threads but they assume the use of a vacuum pump. But you don't get any air bubbles coming past the threads when you pump fluid through with the brake lever or brake pedal, but you might get a little fluid squeezing past the threads. So, no. Teflon tape is not 100% effective and is not necessary.

Me - if I am filling the system from scratch, I will use a vacuum pump just to get fluid into the lines and to maintain a steady flow while I go round the lines tapping and flexing to dislodge trapped air - And then use the traditional bleed method to finish off. But I bought the vacuum pump to compensate for what turned out to be poor technique.

If you are trying to fill the system by repeatedly squeezing the lever with the bleed valve open, then you wont get anywhere. Air will compress easily and that method doesn't get rid of much air - it squeezes a bit out and it immediately gets sucked back in again.
It therefore takes a long time before any feel is obtained at the lever. The old method of having a bleed tube ending in a part filled container of clean fluid helps.

The best technique is to pump the lever with the bleed valve closed. This buids up air pressure in the lines. Hold the lever in so that the pressure cannot escape through the master cylinder, and open the bleed valve to release the pressure. Close the bleed valve and repeat. I fluid starts to emerge, close the bleed valve just before it stops flowing. Repeat.

It doesn't take too long before the fluid reaches the bleed valve and there is no need for teflon tape or speed bleeders.
 
Thanks John for saving me a lot of typing, bleeding hydraulic systems is easier with the correct procedures. On occasion I have had to pump fluid up from the bleeder screws to the master cylinder using a big syringe ( messy though), and don't use to much force or you will have a bigger mess. Cheers G
 
jfheath said:
The issue only arises when using vacuum pumps. This sucks fluid out of the system rather than pushing it out with brake lever pressure. But when you undo the bleeder valve, the cone at the end that forms the seal is no longer in contact and no thread is airtight - so air is sucked past the threads from the outside and in through the hole in the side of the bleeder valve which is at ,the bottom of the threads and above the pointed cone at the end.
Click to expand...
This is interesting, so why does "motion pro check valve" ( manual brake bleed system) state in the instructions to using Teflon tape on the bleeder threads to help prevent air getting past the bleeder threads?
This system does not use a vacuum pump but rather a manual pedal push or brake lever pull to bleed the brakes.


I am very grateful for your detailed explanation. Thank you very much.
 
Thanks everyone for your responses to my questions.
I am of the conclusion that it is a total toss up on whether to seal the threads or just leave them.
I noticed when using the motion pro one-way check valve bleeder this last time I got a tiny stream of air bubbles coming out of the bleeder that seamed to just stay there no matter how many times the lever was pumped or how much fluid was pumped through, The brakes and clutch are solid and I got all the old fluid out of the system, so I am happy.
 
ST-Traveler said:
This is interesting, so why does "motion pro check valve" ( manual brake bleed system) state in the instructions to using Teflon tape on the bleeder threads to help prevent air getting past the bleeder threads?
Click to expand...
With the bleed valve loosened there is a route past the threads for fluid to get out under pressure. I believe that the check valve is after the threads, so in theory, when you release the lever, the slight suction could draw in air past the threads. The manual method gets past this issue by closing the bleed valve before you release the lever.
 
jfheath said:
With the bleed valve loosened there is a route past the threads for fluid to get out under pressure. I believe that the check valve is after the threads, so in theory, when you release the lever, the slight suction could draw in air past the threads. The manual method gets past this issue by closing the bleed valve before you release the lever.
Click to expand...
Thanks that makes since.
Since the motion pro is a check valve, then when pumping the lever without closing the bleeder it is possible for a slight amount air to get past the threads. Pretty much makes the motion pro allow air in a (very small amount) through the threads on the release stroke.
 
I'm still trying to figure how a pressurized system sucks in air. My brain is twisted enough, you all don't need to be f#&king with it....lol
 
St-Gerard said:
One benefit of Teflon tape on the bleeder is it will help prevent the bleeder from seizing in the caliper.
Click to expand...
A question. Has anyone ever seen rusted threads on a bleeder nipple below the edge of the caliper?
Bleeder nipples often show rust above the caliper, but since we loosen the nipples and draw brake fluid (mineral oil) out I assume the threads get a little oil on them. I've not seen rusted threads and figured the tight nipples that I've feared would break off under my wrench were that tight because the previous bleeder (human) had torqued the nipple tighter than necessary. No doubt teflon tape would reduce friction between the caliper's threads and those on the nipple, but would not do anything to reduce the effort to unjam the tapered tip of the nipple from it's mating taper in the caliper.
 
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