Brake Bleeder Thread Sealant?

[NeoJuice]

Folks,

I finally got back from holidays and had some time to work on the truck. I got the hole cut in the floor and my brother helped me bleed the brakes.

Here is a link to my old thread about the residual valve mounting.

http://67-72chevytrucks.com/vboard/s...d.php?t=743831

Bleeding went smoothly and got all the air out and all nice clear fluid with no bubbles on each corner which I was very happy about and no leaks in any of the brake lines I fabricated.

Now onto the problem. All my bleeder screws are tightened up but they're leaking fluid out around the threads (I believe) on all four corners of the truck and down onto the caliper and onto the ground. WTF? I need to verify closer if it is coming from around the threads or out through the bleeder hole.

I'm worried that air might be getting sucked back into the system. The rear calipers are brand new and the front MII front calipers have never had brake fluid in them (brand new).

Should I get new bleeders? like speed bleeders? Researching online people are pro/against Teflon tape. I don't need to be going buying four new calipers.

Thank you for your time.

What are your thoughts?

[mongocanfly]

odd that all 4 are leaking...i assume youve checked to make sure theyre all tight..I'd replace the bleeders to start...they work like a needle and seat..the threads don't really seal...make sure there's no trash/dirt in the bleeder hole that could have gotten behind the bleeders...

[mr48chev]

As Mongocanfly said the threads don't seal anything. It is the seat in the cylinder and the tapered tip of the bleeder screw that do the sealing.

[NeoJuice]

I'll pull the bleeders out and take a closer look for any damage or debris. I didn't really bother checking them before I started to bleed the brakes except to make sure they were all tight.

They were already installed with the calipers so I figured that they would be fine. I wrenched on them hard and they are all tight so I'm not sure why there leaking.

I'll post an update once I have a chance to take a closer look and someone to help me re-bleed the brakes.

I'll also get some new bleeders to rule that out of the equation.

Anyone ever use any kind of sealer? like Permatex 59214 high temp thread sealant?

[mongocanfly]

never had a need to use sealant on the threads...like stated above the threads don't seal...its a needle/seat kind of action. ..

[Black_Sheep]

The taper on the end of the bleeder screw seals against the corresponding taper in the caliper / wheel cylinder casting. Replacing the bleeder screws is the easiest and least expensive option, I would try that first...

[NeoJuice]

Originally Posted by Black_Sheep

The taper on the end of the bleeder screw seals against the corresponding taper in the caliper / wheel cylinder casting. Replacing the bleeder screws is the easiest and least expensive option, I would try that first...

I'll replace the bleeders in the next couple days. I also found this link.


http://www.mityvac.com/pages/info_faq.asp

Just a fyi.

[mongocanfly]

what they're doing is using a vacuum bleeder ...the teflon tape is being used to prevent getting air in the system from around the bleeder screw threads whike the system is under vacuum..the tapes not being used to seal the threads after bleeding. .

[dsraven]

if the fluid is, in fact, coming from around the threads then I would remove the bleeders one at a time and take a look at the tapered seat area on the end of the screw. it should have a nice uniform taper on the end with no grooves or nicks etc. if they are all good then next check the seat area in the bleeder screw hole on the calipers and wheel cylinders. that is a bit more difficult but can be done easier with a small syringe to suck a bit of fluid out of the hole. you gotta be fast here because the system will automatically gravity bleed so more fluid is going to be coming as soon as you suck a bit out. new bleeder screws are cheap so maybe just replace the screws first and see what happens.
some guys will put teflon tape everything simply because they think it helps seal and they may not know any better. like said earlier, bleeders screws seal on the taper and brake lines are classified as an inverted flare fitting so the seal comes from the tapered flare, not the threads. I have heard of a few guys that wrap the threads on brake fittings because it makes them easier to tighten up and get off after a few years, stops rust is the thought.
start by cleaning the area well with brake clean and compressed air (safety glasses) then include a couple of pics of the leak if it is still there. you could try a small piece of clear tubing attached to the bleeder port of the screw, then if it leaks from the bleeder portion it will show up in the hose. if it leaks from the threads it will be apparent and the hose will be dry on the inside.

[my56chevytruck]

As so many have already stated, reading that all 4 bleeders are leaking tells me something ain't right with the bleeders-threads-or seating area?? Never had to use any sealant to seat those I've worked on, but I had ONCE over tightened a bleeder and cracked the threaded area. I changed the bleeder 2 times before finding out it was cracked. As dsraven said, check (1) at a time and I would definitely buy the ones recommended for your application and replace (1) at a time. Keep us posted.

[mr48chev]

That is an absolute new one on me. Sleeved bleeder screws, who would have ever thought about that but the rebuilders probably don't throw much away unless it is totally destroyed.

[NeoJuice]

I got the pictures of the old bleeders for you front and rear. Silver are rear gold are front. (see attached). As you can see one of the rear silver ones was smaller. As I mentioned in the other post how one of the rear calipers was sleeved. The other rear was the correct size but also grooved and leaking.

I've installed new bleeders in the front calipers and rear calipers so hopefully I don't have any leaks when I bleed the brakes again.

Last night I finally got the adjustment of the passenger side rear ebrake caliper done. So now both of them have 1/4" pull before engagement. I still need to hookup my rear brake lines and tighten up the calipers before bleeding again.

I will update the thread after my next bleeding session.

[Steeveedee]

One of two things come to mind, both bad.

1. There isn't a way to "sleeve" the caliper (or rotor) for the bleeder. It might have an insert like a Heli-Coil(R) for the smaller threads. I don't ever recall using a Heli-Coil(R) in a hydraulic system, and I wouldn't want to try. The system is tested to 2000 psi at the factory, and I don't think that they are meant for that application.

2. The smaller bleeder screw isn't necessarily going to get the same seal as the big one, due to possibly even missing the inner edge of the taper. I seriously doubt that they would seal at panic stop pressures.

That's a pretty hack fix, AFAIAC.

[dwcsr]

There are two way to repair a bleeder screw hole as far as I know, one is very similar to an insert that's screwed in and sealed then a bleeder is screwed into that, the other is you tap out the bleeder hole to 1/8 NPT and install a brass screw in bleeder assembly.

Dorman makes the brass one in various sizes. The other I see used on Motorcycles mostly

[my56chevytruck]

that's amazing, to have all 4 bleeders leaking. glad you got it fixed, now on to the driving!!!

[_Ogre]

never use teflon tape on any hydraulic system
even carefully applied teflon can shed teflon threads into the system which then messes with valves
always use dope

ogre was a heavy machine maintenance mechanic in a previous life
it was a firing offence to use teflon tape on any hydraulic system

this is why sensors and fittings now come with pre-applied dope like the red sealant in your pic
on sensors teflon tape can electrically insulate the sensor

[NeoJuice]

So your saying I could use something like the Permatex thread sealer products on the brass fittings? because if so then I'll go pick some up. I'm getting so sick of all these brake issues LOL. I never thought that so much time would be wasted on brakes. Go figure.

http://www.jegs.com/i/Permatex/775/59214/10002/-1

[dwcsr]

Never use sealant of any kind on brake fittings or lines. If it is leaking it means the fitting is defective and should be replace or the flare is bad and should be properly repaired. And no compression fittings either.

[dsraven]

if it is leaking at the pipe thread area of the brass fitting, where there is a red sealant on the threads of the brass, then you may just take the fitting out, check the threads for damage, install some liquid thread sealer and re-install. if it is leaking at the brake line connection to that brass fitting, then first check the flare on the brake line for cracks or distortion, debris etc and also check the seat area in the brass fitting where the flared tube butts up and seals against the brass. you may have an issue there. look for cracks, a bump or line where there may have been a piece of debris on the seat when the line was tightened. this can distort the seat and you will not get a seal and will need a new fitting. also ensure you have the same angle on the two parts, the tube and the brass seat. the brass fitting wouldn't break the bank if you need to replace it, as well as the brake line.
try not to use the tape style pipe thread sealer because it can leave little pieces of the tape flapped out into the fitting and cause issues when it becomes free floating in the brake system. especially if you have to undo the line for some reason. a liquid style, like the red style used on the assembly now, is better. don't use anything on the threads of a flared fitting connection because they are not the sealing area of the fitting. that is done with the flare and seat. the threads simply tighten or loosen the connection. a drop of brake fluid or synthetic brake grease on the threads for lube if you feel you gotta use something, but use sparingly.

[NeoJuice]

Thanks for the input dsraven.

Both residual valves are leaking at the pipe thread area of the brass fitting where the red sealant is on the threads in the picture. If I recall correctly my valve didn't have any sealant on it like in the picture. It was just brass on aluminum.

My flared 3/8-24 fitting that goes into the brass fitting is not leaking and my flare is good.

So I will pick up some thread sealant for the brass fitting. I will also remove and check for any damage.

The leak is right were the arrow is in the picture.

[dsraven]

are you sure the fitting in the res valve is a pipe thread, like the brass fitting, and not a flare fitting or some other thread? best to check the threads inside the res valve and also for damages to the actual res valve if it is an incompatible thread between the two parts.