Should Thread seal tape be used on Pressure Switchs on stop lights?
 

I am replacing a pressure switch on my 1939 Ford Deluxe as it apparently went bad after four months use! Should I use Pipe thread seal tape on it is my question? Thanks!

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

I see no need. JMO

Paul in CT

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Tapered pipe threads that use no gasket should have either sealer or teflon tape carefully applied. Straight threads using a gasket (like copper or aluminum) need no sealer.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Just wondering,......was a sealer used in original production? Not disagreeing with anything said here, just wondering.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Shoebox: I seriously doubt if any sealer was originally used as it would be add cost and be redundant to the functional design of pipe threads. It would be like adding Loctite to a lock washer on the assembly line.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

If anything, use a pipe dope, not tape.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

I think relying on a sealer in that application is false security. the parts should seal as intended or be replaced.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Brake Fluid dissolves Teflon tape. Sealing the threads with any sort of "Pucky" will not work either. In BRAKE lines, it's normally not the threads that do the sealing. The Double FLARE normally does the sealing. In the case of a brake light switch, the threads are usually a TAPERED fit which are designed to seal themselves via a designed interference. If the TAPERED parts do not seal, they are defective, or do not meet spec. DD
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Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

No sealer was ever used on this switch nor is it required.
The switch becoming defective in four months is due to poor quality.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Hmmmmmm . . . I've read a few posts about brake fluid dissolving Teflon/PTFE tape - not sure that I buy that, and I'd like to know more.

Why do I say this? Well, because on high-performance brake systems we frequently use braided stainless steel flex lines and they all have a Teflon/PTFE core. They are considered a superior upgrade to the standard rubber-based lines we've all used.

If brake fluid had a damaging chemical reaction with Teflon/PTFE, there is no way in heck they'd be building/selling these brake lines (and they are used a LOT!).

So the jury is NOT in for me on this question . . .

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

It could be that the China tapered threads are not exactly the same as original US made switches had and need some kind of sealer. I had a situation where I was suspecting the copper washers were not seating when it was in fact, the POS switch threads. I found an old used switch that solved my problem.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

All reply's are appreciated! Thank you. Thank you very much. EP

Note for the record:


When taking the defective switch out I loosened the lock nut behind it and did not tighten it properly until we had bled the brakes. We were on the last wheel and we noticed it was leaking fluid every time I pushed on the pedal to get the air out. Although the car does stop, I feel there may still be some air in the lines, albeit a small amount. The pedal goes about 2/3rd's of the way to the floorboard.


What is normal, acceptable or customary brake pedal travel?


I will bleed the brakes once again just to make sure. Man that is a pain in the neck job! Three out of four of the bleed valves had gotten buggered up so I must replace those valves.


I assume that they are available at an Auto Parts store?


Is there an easy way to bleed the brakes without jacking the car up and removing the wheels?


The problem with the wheels on, was that it is not easy to get to the bleed valve with a wrench. Valves being buggered up too did not help the process of putting a wrench on the bleed valve.

At least I have Brake Lights Now!

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Bring a used bleeder screw to NAPA so they can match the threads, etc. They have numerous sizes in stock. Replace all four. They are cheap.
I don't need to remove the wheels to bleed the brakes. However, I do raise the car and place on stands.

Many years ago (decades) it wasn't unusual for an officer to check your pedal by placing a piece of 2 x 4 at the floor. If the pedal didn't hit the block, you were good to go. Keep in mind, back then, a 2 x 4 was truly 2 x 4.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

So, watch out if you ever see a cop on a Harley carrying lumber. DD
.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Ramblin Reck; I also didn't like the short 1940 Ford brake bleeder screws so I bought longer ones from Speed Bleeder. What a great improvement. Other companies have them also. Just make sure you get the correct thread size. Longer bleeder screws are also great if you use safety hub gizmos.
http://www.speedbleeder.com/

HOW TO USE SPEED BLEEDERS
No special equipment is needed when purging air from the lines with Speed Bleeders. At the front brakes, there isn't a lot of room to attach the drain hose. While not mandatory, a 90 degree fitting makes the job much easier. While I no longer bleed brakes with a vacuum pump, Mityvac includes this handy part with their kit. You will also need some means to depress the brake pedal. This does NOT mean to inflict tales of woe upon it, but rather to physically push the brake pedal, for which a normal human foot works exceedingly well:



Installation of Speed Bleeders is a piece of cake. Remove the old bleeder screws and thread the Speed Bleeders in place. A few drops of brake fluid may spill, but this is not a big deal. Here you can see the drain hose attached to the newly installed Speed Bleeder. Loosen the Speed Bleeder approximately 1/4 turn and slowly depress the brake pedal. Applied fluid pressure will force open the check valve and fluid will drain. I'm using an empty container to catch the old brake fluid for disposal. When the brake pedal is released, line pressure drops and the check valve closes. Repeat the process until all air is purged and then tighten the Speed Bleeder. Move on to the next wheel and repeat. This mimics The Man & A Boy Method of manually opening and closing each bleeder, but is fully automatic and doesn't involve any inappropriate language:



A few precautions are in order during the bleeding process, whether or not Speed Bleeders are used. Follow the service manual to adjust the freeplay in the linkage to the master cylinder. If the freeplay is excessive, the pedal will travel too far before the piston starts to move. This limits the effective travel of the piston. If freeplay is too tight, the piston won't fully retract when not in use. This will limit the amount of fluid from the reservoir entering the piston bore for the next brake application. Once again, brake effectiveness will be reduced. Freeplay is measured at the pedal and is adjusted by changing the length of the pushrod entering the back of the master cylinder:



Adjust the brake shoes to compensate for normal wear. Remember, these brakes are not self-adjusting like on newer vehicles. Adjustment of the brake shoes won't have any effect on the air in the lines, of course, but it will reduce the amount of pedal travel before the shoes contact the drums. The net result is a firmer pedal and better braking action. As a last note, don't let the reservoir run dry during the bleeding process, or entire procedure will have to be repeated. This picture shows the handy remote master cylinder reservoir being replenished. Note the old blanket on the fender to protect against any spills:

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

What I was thinking.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Kube THANKS!

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

19 Fordy THANKS!

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

I've always assumed those switches were NPT (National Pipe Taper) and as such they are designed to be used with some sealant.
NPTF (National Pipe Taper Fuel) has the same basic taper dimensions but the difference is in minor and major diameters & root and crest. NPTF threads form a mechanical seal due to thread crush, so no sealant required with NPTF.

This is what I was told by a fluid engineer.

Re: Should Thread seal tape be used on Pressure Switchs on stop lights?
 

Are you using silicone brake fluid?