Replaced rear brake line on 1997
Wideglide to a Magmun stainless steel line, problem is where the brake light switch has a taper thread and goes into the block I have a small weep from there . Does any one use any type of sealant (brake fluid compatable )on the threads ? Any tighter and I may break the switch threads.

 

Teflon Tape.....

 

Teflon tape is not a sealer,[it's a lubricant]but it might work. The factory used some sort of a red sealer on those,which set up really hard.

 

There is no reason to use any type of sealant on any brake components .
They are a press fit to accept the very high hydraulic pressures of brake components and the actual mounting nuts have nothing to do with this.
Check the compatibilty of your components and ensure that your lines are flaired correctly . There are aftermarket components that require different
types of connections but they are all standardised and easily accessable and very inexpensive.
Take your stuff and questions to any auto. parts store and they will set you right.

 

Looks like that switch is #72023-51E, which remarkably dates it back to 1951! If so we can forget current thinking on sealing it. Unfortunately, while my 1990 manual shows that switch, no mention is made of it, so no help there! If the factory uses anything (it's a long time since I stripped and rebuilt mine) they don't share info that with us.

My inclination is to remove the caliper, strip and clean it (to ensure that female tapered thread is clean and dry) and use loctite.

 

It's been a long time since I replaced a brake line, but if memory serves, I used Loctite "Pipe Sealant With Teflon" for the pipe threads on the stop light switch.

Machinehed, the switch in question is a 1/8 NPT threaded fitting. Pipe fittings must have some sealant or they WILL leak.

That's also what I use on the threads on the fuel petcock (and what Harley recommends).

 

A new 9 dollar switch comes with some sort of red sealant on it and I've never had one leak... I'd just get a new switch and be done with it, they seem to go bad often enough anyways....

ds

 

Sorry but beg to differ ... pipe threads do require a sealant for normal applications but we are talking about brake lines here and that is a whole different matter. A 3000 psi brake line is not " sealed " at the union nut with any type of sealer . The connection from one component to the other is accomplished by a flair on the end of the brake line that is " mashed " into the receiving component by the tourque applied to the union nut . There is no additive applied to the compression nut other than a possible factory applied lock tight ring on its threads.

 

As stated previously , your weep is not repairable by adding sealant to the union nut .
A weep on a brake line component after a service is usually caused by a brake line that has not been set in straight or incompatible parts .
I see that your particular component is a standard unit and does not require the new double crimping procedure or incompatible parts problem etc.
To fix weeping problem , start by loosening all previously attached lines and ensure that they are mating in a straight line to there receiving parts.
Retighten the union nuts and check for leaks .
If leaks persist you must reflair the connecting lines with a flair tool available at any auto shop for $ 20-30 bucks .

 

It looks like there was some red sealer on it but since I took it out of the old block fitting and reinstalled into new block that comes with the Magnum rear brake line. It is NOT the fittings on the m/cyl or the caliper ...its the pipe threads on the switch . may just buy the switch or a thin coat of high temp thread sealant . Thanks for the responses guys