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Old 13-06-2010, 11:01   #1
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Oil Senders & Teflon Tape

Ok, I just rebuilt a new gauge panel and replaced all my senders for Oil Pressure and Oil Low Pressure Alarm. They are both on a bronze "T" from the lower block. Turns out they are leaking around the threads.

Can I use teflon tape on the oil sender threads? This is an attempt to stop the leaks.

I know you can't use it on the Water Temp because it blocks the sender from self grounding. Is it the same for a normally on pressure switch like an oil sender?

I know, I know...................go read the damn instructions.
Well they're on the boat and I'm at home on a Sunday morning.

I appreciate any help.
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Old 13-06-2010, 11:11   #2
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Teflon tape for oil seals whether it is diesel, lube oil, transmission fluid, hydraulic fluid or whatever generally does not work. I use #3 Aviation grade Permatex for oil related seals.

Description: Non-hardening liquid gasket sealant/dressing/coating is a thin, brushable dressing or sealer for close-fitting parts. Suitable for continuous temperatures to 400˚F (204˚C). Resistant to antifreeze, aviation fuels, high-detergent oils and lubricants. Conforms to MIL-S-45180 D. Suggested applications: Gasket coating or sealing close-fitting machined parts.

The sender will ground just fine.

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Old 13-06-2010, 11:17   #3
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Originally Posted by Maddog View Post
... I know you can't use it on the Water Temp because it blocks the sender from self grounding. Is it the same for a normally on pressure switch like an oil sender?
I know, I know...................go read the damn instructions.
Well they're on the boat and I'm at home on a Sunday morning.
I appreciate any help.
Yes, typical oil senders (1 wire) are also body grounded, so you cannot use Teflon.
Instead use blue Permatex (thanks David) or LocTite.
Yes, do read the instructions.
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Old 13-06-2010, 13:24   #4
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Areyou sure the pipe thrreads are the same?

Teflon is NOT to be used for oil or diesel

Silicone is a no-no
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Old 13-06-2010, 13:46   #5
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Quote:
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Ok, I just rebuilt a new gauge panel and replaced all my senders for Oil Pressure and Oil Low Pressure Alarm. They are both on a bronze "T" from the lower block. Turns out they are leaking around the threads...
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Originally Posted by Chief Engineer View Post
Are you sure the pipe thrreads are the same?
Teflon is NOT to be used for oil or diesel
Silicone is a no-no
Sender “T/Y” adapters are very prone to leaking & breakage.
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Old 13-06-2010, 15:46   #6
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Thanks guys - Permatex it is.
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Old 16-07-2010, 00:16   #7
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Just got back from the boat and the permatex did the trick.

Thanks
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Old 16-07-2010, 06:04   #8
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Quote:
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Can I use teflon tape on the oil sender threads? This is an attempt to stop the leaks.

I know you can't use it on the Water Temp because it blocks the sender from self grounding. Is it the same for a normally on pressure switch like an oil sender?
It's been said, but teflon tape will insulate the sender from the block and break the electrical circuit.

It has nothing to do with diesel, oil, or whatever, the sender must make electrical contact with the block to complete the circuit.
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Old 16-07-2010, 06:59   #9
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This is true, many engine block sensors use their threads as a ground.

It is also very true that oil can leak slowly past Teflon tape wound around threads. I have seen it from somebody who did this with a diesel fuel line.
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Old 16-07-2010, 08:01   #10
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This is true, many engine block sensors use their threads as a ground..
Any thing with only one wire attached is using the engine, fuel tank, transmission, etc. as a ground.
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Old 16-07-2010, 08:04   #11
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Any thing with only one wire attached is using the engine, fuel tank, transmission, etc. as a ground.
Indeed.

AND:

Teflon tape is to be used only on fittings that seal on the threads, ie: Tapered Jointing threads such as type NPT or BSPT/Whitworth.

Do NOT use tape on Fastening threaded fittings, that seal at the tip or at the bolt head. So banjo, AN/jic/37 degree, bubble flare, inverted flare, 45 degree flare and a host of others are designed to seal without tape.
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Old 16-07-2010, 12:15   #12
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Any thing with only one wire attached is using the engine, fuel tank, transmission, etc. as a ground.
I'll go ahead and add that any plumbing that's bonded such as a tailpiece on a seacock should be sealed with pipe dope, not teflon tape.
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