Topic: oil pressure switch replacement- teflon tape?

[CoachDoc]

Is a teflon tape thread wrap a good idea when replacing a leaking oil pressure switch?  ('74 550)

[SOHC Digger]

Yes.  Teflon tape is a good idea anytime you are trying to seal pipe-thread.

[new2bikes-again]

I didn't use teflon when I replaced mine two months ago. I didn't because mine had an inverted flare on the end. It hasn't leaked after 200mi.

You might want to look at your's to see if it has a flare.

[70CB750]

I use the pink plumber's tape, thicker than the white one.

[kghost]

Just a quick word of instruction.......

Teflon tape is used to get the pipe fitting further into its bore......

It's not designed to seal.

" The use of PTFE tape in tapered pipe threads performs a lubricating function, which more easily allows the threads to be screwed together, to the point of deformation, which is what creates the seal."

http://en.wikipedia.org/wiki/Thread_seal_tape

[crazypj]

I've never used it on my 550 and I've had to change several oil pressure switches.
Just make sure to use thinner oil or spend a long time warming motor up, the switch placement is real poor and the leaks are generally from the top cap being over pressurised

[CoachDoc]

Nice variety of opinions re. the tape. I don't usually use any, but this fitting definitely looks like pipe thread, so it may be a good idea.

[Powderman]

Teflon paste may be a better option for sealing.

[Stoli]

I fixed a l leaky switch with some stuff I found at my local auto parts store. Made by permatex if I recall correctly. Forgot what it is called but it was specifically intended to seal the threads of oil sensors, etc.

[kghost]

None of the tapes or goop seal!

It a lubrication that allows easier thread sealing.

Use it. But it's not what makes the seal.

[tlbranth]

I use a lot of Teflon tape in plumbing applications. When you disassemble a joint that's been sealed with teflon, you get a plume of skinny bits of the stuff all over the place. I'd be afraid of some of this getting into the oil line and mucking things up so I'd probably go old-school and use Permatex High Tack or something similar. It's always worked for me in the past.

[CoachDoc]

I use a lot of Teflon tape in plumbing applications. When you disassemble a joint that's been sealed with teflon, you get a plume of skinny bits of the stuff all over the place. I'd be afraid of some of this getting into the oil line and mucking things up ....................

I was thinking that the teflon paste would be likely to cause some problems if a bit found it's way into an oil passage, but I'm sure you're right that the tape could do the same thing.

[bjbuchanan]

The permatex is the the super black one. It is resistant to oil, and in my experience, impervious to it

[kghost]

I use a lot of Teflon tape in plumbing applications. When you disassemble a joint that's been sealed with teflon, you get a plume of skinny bits of the stuff all over the place. I'd be afraid of some of this getting into the oil line and mucking things up ....................

I was thinking that the teflon paste would be likely to cause some problems if a bit found it's way into an oil passage, but I'm sure you're right that the tape could do the same thing.

Don't put it over the ends of the threads.......

[Johnie]

Changed a ton of these same type oil sensors in cars and we never used any tape do to the flare. Never had a leak. Do what makes you feel good.

[Powderman]

None of the tapes or goop seal!

It a lubrication that allows easier thread sealing.

Use it. But it's not what makes the seal.

so this is all false advertising by the manufacturer?

   
Loctite® PST® Pipe Sealant with Teflon
   
   
Locks and seals threaded fittings. Resists leakage, vibration loosening, moisture, hydraulic fluids and diesel fuels. Lubricates threads for easy assembly and disassembly. Won't shred or wear like Teflon tape. Repositionable up to 24 hours.

For head bolts into through holes, oil PSI sending units/sensors, oil and coolant lines, fuel fittings, rear axle fill plug, brake/power steering fittings. Teflon is Registered. TM is DuPont.

[Powderman]

Changed a ton of these same type oil sensors in cars and we never used any tape do to the flare. Never had a leak. Do what makes you feel good.

Flare fittings use a different method to seal than a pipe thread.

[Powderman]

Just a quick word of instruction.......

Teflon tape is used to get the pipe fitting further into its bore......

It's not designed to seal.

" The use of PTFE tape in tapered pipe threads performs a lubricating function, which more easily allows the threads to be screwed together, to the point of deformation, which is what creates the seal."

http://en.wikipedia.org/wiki/Thread_seal_tape

If you read the wiki post further you would have seen that it is commonly used as a thread sealer.

Teflon is a brand name and Teflon does not make a Teflon Thread Sealer tape. Most time Teflon tape refers to common PTFE thread sealing tape specifically made for sealing threads.

[Dave Voss]

The oil pressure switch needs a reliable ground path to function electrically, that ground path is the threads on the switch and the mating threads in the engine, and so covering those threads with tape, paste, etc. is not recommended.  Typically, nothing extra is required to prevent leaks at the oil pressure switch.

[Powderman]

The oil pressure switch needs a reliable ground path to function electrically, that ground path is the threads on the switch and the mating threads in the engine, and so covering those threads with tape, paste, etc. is not recommended.  Typically, nothing extra is required to prevent leaks at the oil pressure switch.

I seriously doubt using a thread sealer paste would completely isolate the sensor from any metal contact required for ground.

[Powderman]

If your sending unit is like this it is a pipe thread and is sealed by pressure on the threads as it is tightened. It should seal tight by tightening it alone until it seals. If it is bottoming out in the hole before this happens your hole has been worn from much use or replacements. It is not intended to seal with a flare on the unit. Those type units that seal with a flare have parallel threads and not a tapered pipe thread. 

[Dave Voss]

I seriously doubt using a thread sealer paste would completely isolate the sensor from any metal contact required for ground.

You're right, it probably wouldn't, but the factory didn't use any sealer, and it shouldn't be necessary during replacement either, unless the thread forms are damaged.

[Powderman]

I seriously doubt using a thread sealer paste would completely isolate the sensor from any metal contact required for ground.

You're right, it probably wouldn't, but the factory didn't use any sealer, and it shouldn't be necessary during replacement either, unless the thread forms are damaged.

You are correct. I mentioned the cause of leaks are from replacements and you will seldom have a factory installed unit that leaks.

[excellrec]

Speaking of these, does anyone know off hand what the diameter and thread pitch is?  I have been meaning to replace my unused one with an oil temp sensor.

[Powderman]

Speaking of these, does anyone know off hand what the diameter and thread pitch is?  I have been meaning to replace my unused one with an oil temp sensor.

1/8"/27 pipe thread.
 Just get one with a 1/8" pipe thread, it's a pretty standard size.