Teflon Tape on Bleeder Screws

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I think I will be switching to a vacuum bleeder in the future due to versatility.

On the two previous occasions that I used a vacuum bleeder, I experienced a low pedal issue on one of the cars. I suspect this is due to a combination of opening the screw too far and sucking air past the threads.

I read somewhere that wrapping the bleeder screw threads with teflon tape will cure the issue of sucking air past the threads. Has anyone experienced success with this?

Thanks.
 
I have used teflon on the threads with success but if I know there isn't (much) air in the system I ignore the bubbles and make sure I bleed plenty of fluid through that bleeder.
 
teflon tape can leave a mess. Im not sure Id want it on the threads. I'd use pressure or a set of speedbleeders or something else, if I were you.

Not sure if teflon tape could get into the bore, or what it would do, but I dont care to find out when there are better ways to bleed brakes.

Why are you sold on vacuum?
 
One or two turns of teflon tape shouldn't hurt anything if it doesn't extend past the bottom of the threads. As an alternative, how about letting it gravity bleed for a bit after the vacuum bleed?
 
I've had good luck using TT on the bleeders. The biggest advantage is, it seems to keep the bleeders from corroding up and allows you to break them loose again if you need to re-bleed for any reason.
 
I don't think it's necessary to put teflon on the threads or seal them. It doesn't matter that air gets around the bleeder threads or that the bleeder was opened wide. The air won't go downhill of the bleeder seat and should instead draw around and exit the bleeder. That's why gravity bleeding can work and the bleeder can be left opened while the air get pushed out.

I think when gravity bleeding or when using a vacuum bleeding the master cylinder cap mustt be left off. If the cap is on a lower pressure or void could develop back in the brake system and draw in some air.
 
I use a vacuum bleeder. I like to smear a little thread sealant (I use Teflon based) around the base of the bleeder where it screws into the caliper. For me this is much easier than removing bleeder to wrap it with Teflon tape and it works great.
 
I never understood how you get teflon tape on the thread without taking the bleeder off completely. As far as I am concerned, why would I want to take off the bleeder and expose the line to the air?
 
I agree with "mechanicx" I have a Mityvac hand pump for bleeding brakes almost always get air around the bleeder screw but as long as there is vac. on the bleeder no air will go into the system.

I have tried teflon tape and brake grease (to no avail) to eliminate the bubbles in the old fluid when bleeding brakes. The problem with wrapping or greasing the threads is that once you tighten the bleeder and loosen it again the seal is gone. Now I don't worry about it because the air is not getting in the braking system just the recovery bottle.

In fact, most of the time now I just gravity bleed. The best method is to put some clear tubing on the bleeder and route it up at the angle of the bleeder for a few inches then down into the drain bottle. Take the reservoir cap off and then crack the bleeder, fluid will fill up in the hose then drain down into the bottle. There is always fluid at the bleed screw opening to prevent air from getting in and its possible that the siphon effect helps pull fluid through the system.
 
Originally Posted By: JamesBond
I agree with "mechanicx" I have a Mityvac hand pump for bleeding brakes almost always get air around the bleeder screw but as long as there is vac. on the bleeder no air will go into the system.

I have tried teflon tape and brake grease (to no avail) to eliminate the bubbles in the old fluid when bleeding brakes. The problem with wrapping or greasing the threads is that once you tighten the bleeder and loosen it again the seal is gone. Now I don't worry about it because the air is not getting in the braking system just the recovery bottle.

In fact, most of the time now I just gravity bleed. The best method is to put some clear tubing on the bleeder and route it up at the angle of the bleeder for a few inches then down into the drain bottle. Take the reservoir cap off and then crack the bleeder, fluid will fill up in the hose then drain down into the bottle. There is always fluid at the bleed screw opening to prevent air from getting in and its possible that the siphon effect helps pull fluid through the system.



To really prevent air from getting sucked in around the bleeder screw threads, you need to elevate the waste fluid bottle above the level of the bleeder screw. This ensures above atmospheric pressure inside the bleeder screw and hence no air will be sucked in. If the hose is just run up a few inches and then down again below the level of the bleeder screw, the siphon effect could create a slight vacuum at the bleeder if the flow of fluid from the caliper is somewhat restricted.
 
There never is a reason to put tap on the bleeder screws. If you got air in the lines it's because you opened it too far or your bleeder is not providing enough pressure.
 
Originally Posted By: Scott_Tucker
There never is a reason to put tap on the bleeder screws. If you got air in the lines it's because you opened it too far or your bleeder is not providing enough pressure.


Well jeah! But when one chooses to vacuum bleed the pressure is less than 0" gauge. The relative pressure is negative and can draw a small amount of air in. Any positive pressure bleesing including gravity bleeding which produces a few inches of water gauge pressure will get rid of that last little bit of air in just a few seconds. If someone hasn't ever actually seen a bleeder screw in its entirety at thought about how it works, this is not obvious. The teflon tape may well act as a temporary seal during a vacuum bleed to prevent this small amount of air entering at the bleeder valve allowing a successful bleed without a positive pressure stage. I wouldn't call it the best way or the easiest way, but it will usually work and won't hurt anything. It also won't help with any problem of air entering between the master cylinder and the fluid reservoir (yes, this can happen in some circumstances) or through a block type proportioning valve (very rare) during a vacuum bleed.
 
I tried it for the reasons that you mention. It works just fine.

I can't say I ever experienced getting air into the system without it, but I did have the fear that I wasn't getting the job done right due to the thread leakage. The process was much slower and laborious without the tape also.
 
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I use a Vacula vacuum bleeder and it does draw air through the bleeder screw threads when the bleeder is open. But those bleeder screw air bubbles, in the clear bleeder hose, are distinguishable because they are small and almost uniformly spaced close together. On the other hand, bubbles of air emerging from the brake lines are larger and irregularly spaced. I just keep the vacuum on until I get nothing but the little, uniformly spaced bubbles in the line. That technique has worked for the ten years I have been using the Vacula. Try it, you'll recognize the different bubbles.
 
Teflon tape, installed very carefully on conventional bleeder screws, is a huge help.

First off, it totally prevents the bleeder screw from rusting in place and breaking off 4 years down the road when you finally decide to bleed the brakes.

Second, it does "help" seal and somewhat prevents air from being introduced via the threads, during a "backyard" brake bleed.

The bottom line is quite positive. Just install the tape very carefully, prior to installing the new calipers.
 
Tape will do nothing for extraneous leaking during a bleed. Threads are AFTER the seat.
Bad technique IS a brake bleeding problem, however.

I would not use T tape on a brake bleeder fitting for another reason - it is very soft and has the potential to loosen the bleeder's seating . What is tight may be loose later.

There are reasons that NO mfr ever uses T tape on bleeder screws.
 
Originally Posted By: SLCraig
Zero need for teflon tape. A 2 person bleed and no teflon tape and you're good to go. Works every time.


Them's fight'n words! Around here everybody knows you need a (minimum) $50 apparatus or several hours to bleed brakes.
 
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