Teflon Tape on Oil Drain Plug and bilge drain plug

[Adam1]

I recently changed my oil drain plug/ bilge drain plug tether. With the oil drain plug tightly connected to the oil drain hose, I'm seeing oil around the plug. I'm wondering if I should apply teflon tape on the oil drain plug. Are there pros and cons to using teflon tape on the oil drain plug and the bilge drain plug?

 

[Adam1]

Thinking about this, it dawned on me that the teflon tape on the bilge drain plug will impair the continuity of the ground circuit between the drain flange and plug effectively isolating the plug. Corrosion will likely result on the plug since the mercathode circuit would be compromised.

 

[peterkvs]

I use Perfect Seal (Mercury brand) or Permatex Aviation Gasket Maket #3 which appears to be the same stuff. It's basically a non hardening sealer that inhibits galvanic corosion, works as an anti-seize, but still allows metal to metal contact. It's great stuff. 100% water and oil proof. I've never found it anywhere locally, but it's easy to get online.

Pete

 

[Adam1]

Thanks Pete for the info on Perfect Seal. I'll look into it.

 

[JVM225]

Don't know about putting anything on the oil drain plug. My oil gets pulled out of the dipstick tubes, but I never used anything on any of my cars over the years and never had any problems.
I do put a coating of silicone on the threads for the bilge drain plug before putting it in. Probably not needed since it has pipe threads, but I don't like to muscle it too tight and I put the silicone to seal the threads rather than giving it that extra little bit when I tighten it.

 

[Steve S]

Working as an application engineer for a tap thread manufacturer, allow a short dissertation on pipe threads:

NPT - "National Pipe Thread" is one of the standards for tapered pipe threads. The taper is 3/4" per foot of length. However a standard NPT thread is not a complete self sealing thread. This is because the crests and roots of the thread are truncated (like a standard tap) meaning there are "flats" at the crests and roots of the threads. This allows a very nice trapezoidal area to allow the fluid to escape the connection. When plumbers tape or silcone putty etc is used it is not to lock the flanks of the thread as those areas end up in a tight interference fit but to fill in the gaps at the roots and the crests of the threads.

NPTF - "National Pipe Tap Fuel" is very similar to an NPT tap except it is designed without the truncation's so the roots and crests of the mating parts "Crush" together creating a mechanical seal. This is commonly referred to as a "Dry Seal" thread. One note - once a plug has been used in a dry seal application, it should either be replaced with a new plug or tape or plumbers putty should be used to insure a proper seal. The edges can only crush into a shape one time.

NPS and NPSM are straight threads used for low pressure fittings.

Steve

 

[Adam1]

A thought came to mind - The threads on the oil drain plug may not be properly machined resulting in the observed leak. I will try another plug to see if that helps.

Thanks everyone for your help.