rear brake light presure switch

[worker]

when changing pressure switch should you Teflon tape the threads

[Scotty]

I don't use teflon tape anywhere on a Harley as it has no threads on the bike designed for teflon tape.
Having said that I do use some Loctite 567 which is a liquid sealant never had any problems.
YMMV

[darylnj]

i installed without sealant and it leaked so i used leak lock

[Norton Commando]

Teflon tape may be used on any NPT threads on Harleys. Start to wind your tape (2) threads from the end of the fitting and wind the tape clockwise when viewed from the end of the fitting.

Jason

[Scotty]

Teflon tape may be used on any NPT threads on Harleys. Start to wind your tape (2) threads from the end of the fitting and wind the tape clockwise when viewed from the end of the fitting.

Jason

Funny because the service manual calls for "Apply Loctite Pipe Sealant with Teflon 565 to threads of rear stoplight switch" and not teflon tape and there is a reason for it.

[Deye76]

I use Gasoila, thread sealant. Compatible with brake fluid.

[Norton Commando]

Teflon tape may be used on any NPT threads on Harleys. Start to wind your tape (2) threads from the end of the fitting and wind the tape clockwise when viewed from the end of the fitting.

Jason

Funny because the service manual calls for "Apply Loctite Pipe Sealant with Teflon 565 to threads of rear stoplight switch" and not teflon tape and there is a reason for it.

The reason liquid sealant is recommended is because many folks do not know how to properly apply Teflon tape. The tape should be started two (2) threads from the end of the fitting.  In other words, the first two threads are bare, which prevents Teflon tape from being cut by the threads and getting into whatever system you are trying to seal. If properly applied Teflon tape will work fine for sealing the NPT threads on the rear stoplight switch.

Jason

[Burnout]

Blue locktite works as a pipe sealer also but you must get things clean before applying.

[Scotty]

Teflon tape may be used on any NPT threads on Harleys. Start to wind your tape (2) threads from the end of the fitting and wind the tape clockwise when viewed from the end of the fitting.

Jason

Funny because the service manual calls for "Apply Loctite Pipe Sealant with Teflon 565 to threads of rear stoplight switch" and not teflon tape and there is a reason for it.

The reason liquid sealant is recommended is because many folks do not know how to properly apply Teflon tape. The tape should be started two (2) threads from the end of the fitting.  In other words, the first two threads are bare, which prevents Teflon tape from being cut by the threads and getting into whatever system you are trying to seal. If properly applied Teflon tape will work fine for sealing the NPT threads on the rear stoplight switch.

Jason

The reason teflon tape is not used is it might be clean and tight the first time but when removed leaves small pieces of it self behind which if caught in a brake system can cause all sorts of issues. Just look in the filter of a water system that is after a repaired section where teflon tape is used. No mechanic who values thier customers would ever use teflon on a brake system ever.

[Norton Commando]

Teflon tape may be used on any NPT threads on Harleys. Start to wind your tape (2) threads from the end of the fitting and wind the tape clockwise when viewed from the end of the fitting.

Jason

Funny because the service manual calls for "Apply Loctite Pipe Sealant with Teflon 565 to threads of rear stoplight switch" and not teflon tape and there is a reason for it.

The reason liquid sealant is recommended is because many folks do not know how to properly apply Teflon tape. The tape should be started two (2) threads from the end of the fitting.  In other words, the first two threads are bare, which prevents Teflon tape from being cut by the threads and getting into whatever system you are trying to seal. If properly applied Teflon tape will work fine for sealing the NPT threads on the rear stoplight switch.

Jason

The reason teflon tape is not used is it might be clean and tight the first time but when removed leaves small pieces of it self behind which if caught in a brake system can cause all sorts of issues. Just look in the filter of a water system that is after a repaired section where teflon tape is used. No mechanic who values thier customers would ever use teflon on a brake system ever.

Ok, you win!!!

Jason

[Scotty]

It's not a matter of winning, this is a technical forum and giving advice can take many levels and I wanted the OP to have as much as information as possible.
I know some people have been doing things the wrong way for 30 years and get away with it but some people seem to get caught out every time.
If he takes your advice at least my conscience is clear if he has any issues down the road.

[Deye76]

I can't remember taking apart a factory installed brake line, or brake switch and finding teflon tape.
Aftermarket switch, all bets off.

[Norton Commando]

I can't remember taking apart a factory installed brake line, and finding teflon tape.

A "brake line" fitting typically comprises a parallel thread and relies on the flared end of the tubing for a seal.  No Teflon tape or pipe sealant should be used for this particular application. However, the brake light pressure switch on most if not all EVOs, utilizes an NPT (national pipe thread) which is a tapered thread-interference fit. These threads rely on Teflon tape or pipe dope (thread sealant) to assist in sealing. Some folks believe that a slug of pipe sealant will not contaminant the brake's hydraulic system, hence their recommendation to use sealant over Teflon tape. I have designed and maintained hundreds of hydraulic control systems with pressures ranging from 3,000 to 5,000 psi and Teflon tape or thread sealant will work fine for NPT threads. In the field I often used tape followed by a wipe of thread sealant (belt and suspenders) for maintenance and repairs. I have never experienced a hydraulic system failure, owing to a glob of thread sealant or a fleck of Teflon tape in the system.   

Best,

Jason

[Deye76]

I edited my post. Aftermarket switch as stated I use Gasoila sealant. Teflon tape didn't cut it. Just went through all this on my FXR.

[Scotty]

A "brake line" fitting typically comprises a parallel thread and relies on the flared end of the tubing for a seal.  No Teflon tape or pipe sealant should be used for this particular application. However, the brake light pressure switch on most if not all EVOs, utilizes an NPT (national pipe thread) which is a tapered thread-interference fit. These threads rely on Teflon tape or pipe dope (thread sealant) to assist in sealing. Some folks believe that a slug of pipe sealant will not contaminant the brake's hydraulic system, hence their recommendation to use sealant over Teflon tape. I have designed and maintained hundreds of hydraulic control systems with pressures ranging from 3,000 to 5,000 psi and Teflon tape or thread sealant will work fine for NPT threads. In the field I often used tape followed by a wipe of thread sealant (belt and suspenders) for maintenance and repairs. I have never experienced a hydraulic system failure, owing to a glob of thread sealant or a fleck of Teflon tape in the system.

I don't use globs or slugs of pipe sealant I use a carefully controlled amount on every brake system I do.
Using words to assume someone is using a product incorrectly like glob and slug is just plain stupid.
Just because you have never seen a piece of teflon tape block up a master cylinder does not mean it does not happen.

[Heatnbeat]

I'm with Scotty. Years back I worked on some pneumatic systems and they forbid the use of tape. Even if you are careful applying i,t when the fitting is removed/replaced there is tape in the threads and it can be pushed in as the fitting is screwed in. The other problem with teflon is it reduces friction to the point where you can over tighten things. Aluminum intake manifolds have a sticker warning to not use tape on the pipe threadf fittings, too many guys split the boss by running the tapered fitting in too far.