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Wed Mar 28, 2007 5:57 am

Is it me or is the quality of some brake hoses extremely bad. I have changed front rubber hoses on my 64 bug twice now and again I notice I have a leak from the front rubber hose. This has happened in a period of about 2 yrs. One thing I've noticed is excessive threads on the end of the hose after tightening to the wheel cylinder. Could there be a mis match of hose to wheel cylinder?

Wed Mar 28, 2007 9:08 am

Where on the hose did the leak occur? Was it at the junction of the rubber and the metal fitting? A leak there would show poor quailty in assembly but not necessarily in materials.

As for the number of threads on the end of the fitting, it makes no difference. The fitting is supposed to be a tapered thread which seals as it is tightened and it will not go all the way to the bottom of the threads when properly torqued. If it leaks there you need to check three situations:

1) It's not tapered. It bottoms out in the female part of the wheel cylinder but does not seal properly.
2) It's not tight enough. Hard to get a torque reading on this type of fitting but it should be tightened very well in the cylinder.
3) You should wrap Teflon tape on the end of the fitting. Never hurts to do so.

Wed Mar 28, 2007 9:21 am

"You should wrap Teflon tape on the end of the fitting"

I have not heard this advice before. Do we know that brake fluid won't degrade the tape?

Wed Mar 28, 2007 10:07 am

I've found the biggest difference is the quality of non-German vs. German made hoses. I've never had a similar problem with German hoses.....and German wheel cylinders. All bets are off if either side is Brazilian :shock:

Wed Mar 28, 2007 3:00 pm

Teflon tape should not be used in the presence of any petroleum product. The base material is a simple plastic and it will fall apart after some time.

Wed Mar 28, 2007 3:14 pm

KTPhil wrote: "You should wrap Teflon tape on the end of the fitting"

I have not heard this advice before. Do we know that brake fluid won't degrade the tape?

Teflon is used in many brake lines.

For example:
http://www.powerbrake.co.za/pages/hoses.htm
http://www.gmgracing.com/other_brakes.shtml

Or here's a more product-neutral document (just serch for teflon):
http://www.bobbyarchermotorsports.com/pdf_2848_2.pdf

Wed Mar 28, 2007 4:14 pm

I am not sure if these parts are from Brazil or not and right now I'm not exactly sure where the leak is coming from. However the first set of hoses had very small holes in the rubber and it was like they were sweating or something. When I bought the second set I made sure they were of a different brand and DOT approved. When it comes to brakes there should be very high standards no matter who makes these things! I will attempt to locate where the leak is coming from and the manufacturer of these particular hoses. I should also easily determine if there is a taper in the threads. Thanks for the information. I'll post the manufacturer if I can determine that.

Wed Mar 28, 2007 4:59 pm

PTFE or teflon tape is for pipe threads only. For flare fittings, the flare is deformed slightly when tightened to make a circular seal around the "cone". Plumbing and gas line ferrules also deform slightly, no PTFE tape used there except for pipe threads.

Wed Mar 28, 2007 5:02 pm

PTFE or teflon tape is for pipe threads only. For flare fittings, the flare is deformed slightly when tightened to make a circular seal around the "cone". Plumbing and gas line ferrules also deform slightly, no PTFE tape used there except for pipe threads.

Thu Mar 29, 2007 11:10 am

Anyone try stainless steel line on their VW?

Thu Mar 29, 2007 12:01 pm

Stainless is great stuff. It resists corrosion better that the plain steel.

And to KTPhil:
Good question about the PTFE tape and brake fluid.

And to robgoudy:
If robgoudy could cite his source it would be appreciated.

My thoughts were that since Teflon is a pretty inert substance - after all, cooking utensils are coated with the stuff - it shouldn't react with the chemicals in brake fluid. And as I've used it over the years, I've found that it doesn't seem to react.

In researching a number of brake manufacturers and fluid power manufacturers I couldn't find any warnings about breakdown of the tape itself. In fact, Wilwood and a few other brake manufacturers stated in their install instructions to use some at the outlet of the master cylinder. There was a warning about not using it anywhere else but no reason was given.

The only reason that seemed consistent among fluid power manufacturers was that pieces of the tape could break off and clog passages in the equipment.

In our case I don't see that happening. The passages in the wheel cylinders for drum brakes are pretty large. Discs might be another story.

The upshot is that the taper threads on a hose end should seal when tightened properly. I look upon the teflon as a little added insurance.

Thu Mar 29, 2007 12:24 pm

I was taught in Machinery Technician School (USCG) that teflon tape is for plumbing. It is only to be used as an anti-seize, in fact this is what it is marketed as. I was taught that the tape itself is not made of teflon but is a teflon impregnated plastic. If the fitting is leaking then the fitting itself should be repaired. Any kind of sealant would only be a band-aid. Especially in a braking system with very high pressures and a solvent like fluid running through it. I have seen plenty of fuel fittings leak with teflon tape.

Fri Mar 30, 2007 7:12 am

Thanks, robgoudy. Point noted.

Sat Mar 31, 2007 7:15 pm

robgoudy wrote: Teflon tape should not be used in the presence of any petroleum product. The base material is a simple plastic and it will fall apart after some time.

Oh really?????? And where did you come up with this information? I'm 99.999% certain that your statement is bogus. :roll:

Sat Mar 31, 2007 7:23 pm

Bottom line with teflon tape is this: it's to be used on any threaded connection that's seal relies solely on the threads, not having a flare or an o-ring seal present. I get my information from 10 years in the hydraulic hose and fitting business. In the case of pipe thread (NPT), the threads crush when assembled, but there is still a leak path present. The teflon tape, or other thread sealant is used to fill the void present, thus finalizing the seal. Teflon tape is fine to use with brake fluid, fuels, oils, even sulfuric acid. Teflon is killer stuff! The tape isn't my favorite for any NPT connection, but it does the trick. Many people get themselves in trouble with it, by not knowing how to use it. Start the tape 1-2 threads from the end, so it doesn't shred into your brake or fuel system. Looking at the threaded fitting from the end, the tape should be instaled in a CCW fashion, so the tail of the piece installed is trailing, not leading. If it leads, it can bird nest and not stay on the fitting. only 2-3 wraps are required. Any more, and you can split tapered NPT fittings real fast. Hope this all makes sense. :wink:

Sun Apr 01, 2007 4:09 pm

Quote: Oh really?????? And where did you come up with this information?

I was certain that I already answered that question.

Quote: In the case of pipe thread (NPT), the threads crush when assembled, but there is still a leak path present.

The question here should be "where did this leak path come from in the braking system of a vehicle that I will be driving my daughter around in?"

Sun Apr 01, 2007 9:47 pm

No, you never mentioned your sourse. The leak path is a ntural thing with NPT threads. look for a diagram online. If you take your fingers, and put them together one inbetween the other, you can get a sense of how NPT works. The threads interlock, and crush together. When they crush, the void is not completely sealed up......hence the leak path. THe thread sealant fills this void, making the seal complete. No worries about driving your kid around.......it's the installers responsibility to install the fittings right, not the thread designer. NPT is used in 10k psi applications daily........it works.

Mon Apr 02, 2007 3:13 am

KPottorff wrote: Where on the hose did the leak occur? Was it at the junction of the rubber and the metal fitting? A leak there would show poor quailty in assembly but not necessarily in materials.

As for the number of threads on the end of the fitting, it makes no difference. The fitting is supposed to be a tapered thread
SEATS ON A MACHINED SEAT
not tapered which seals as it is tightened and it will not go all the way to the bottom of the threads when properly torqued. If it leaks there you need to check three situations:

1) It's not tapered. It bottoms out in the female part of the wheel cylinder but does not seal properly.
2) It's not tight enough. Hard to get a torque reading on this type of fitting but it should be tightened very well in the cylinder.
3) You should wrap Teflon tape on the end of the fitting
Do Not Do This
. Never hurts to do so.

Stainless Steel Teflon Lined DOT approved brake hoses are availible.

Mon Apr 02, 2007 3:22 am

#1- the ends of fittings are not tapered. #2- the end of hose fitting "crushes/ slightly deforms" to form a seal. i am willing to bet that anyone using teflon tape on brake hose fittings also uses silicon on a vw engine. this person can build very good vw motors,but should never assemble a vw engine. the 4 places that silicon is used on a vw engine is #1 cylinder to spigot seat,#2 cyl. to spigot seat,#3 cyl. to spigot seat and #4 cyl. to spigot seat. <-- period.

Mon Apr 02, 2007 6:54 am

If the fitting end of the hose is a 10mmx1.0 thread, and fits directly into the OEM master cylinder, wheel cylinders, or stock hard lines......it's not a tapered fitting. It has what is called a bubble flare. The flares are not supposed to distort. The flare takes place 1/2 way up the cone (just about dead center line). If it were to distort, chances are it's over tightened. Once they're over tightened, both sides of the connection need to be replaced if it won't seal any longer.