1998 civic, the fuel filter fitting. It's a threaded metal line with a copper washer. It's just seeps but I can't get it to stop. Can you use teflon tape on gas line or will it dissolve? Any other ideas?

Could it just need a new copper washer? Honda is fond of disposable/1-time-use washers.

Tried two new washers, same results

Teflon tape will not and is not designed to provide a seal.

Thread seal tape — commonly known as "Teflon tape", "PTFE tape" or "plumber's tape" — is a polytetrafluoroethylene (PTFE) film cut to specified widths for use in sealing pipe threads. The tape is wrapped around the exposed threads of a pipe before it is screwed into place. Since the PTFE is malleable, deformable and impermeable, it acts a little like putty under compression, being forced into small gaps between threads in order to create an air- and watertight seal when threaded into a joint. The tape is commonly used commercially in pressurized water systems, such as central heating systems, as well as in air compression equipment and thread joints with coarse threads.

One of the defining characteristics of PTFE is how good it is at defeating friction. 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 majority, if not all, of the seal.


I would say it has some sealing properties

Perhaps you should read this sentence a little more thoroughly...

It's sealing properties are such that it enables deformation hence creating a seal. What is in question? Metal to teflon allows greater torque to be applied than metal to metal is the way I understand it. Correct?

When I have leaky threaded PVC fittings, I always fix them with teflon tape.

Most high-pressure connections incorporate some sort of compression seal. Teflon may help, but it would only be a 'bandaid'. Not sure how the 'copper washer' seal works, but assuming it normally does, then the problem could be the steel line has small nick, ding or crack, or the filter itself is allowing the seeping, for whatever reason. You might try a new filter. If it still leaks, your line is probably damaged...

I read the sentence to mean the deformation of the pipe threads as joint is tightened to tapered threads that provides the majority of the seal...not the tape. The tape provide lubrication to allow the joint to be pulled up tighter onto the taper portion of the threads. It does also fill in gaps/air spaces within the joint.

I would not use Teflon tape. No one uses Teflon tape on fuel line fittings. What I would do is dry the tightened connection, have a very bright light and a good view of the connection (a mirror sometimes helps) while a helper turns the key to the run position (don't crank) to prime the system and hopefully you can see EXACTLY where the leak is. You may have to do this several times. That said, the banjo-style connection is usually troubl-free. Don't be afraid to hike yer skirt up and put some torque on that bolt!

Thanks CNY, I think the fitting is bottoming out so you can't torgue it anymore. Perhaps I will try two washers so I can torque it more.

If the fitting is bottoming out, something is wrong! I don't recommend 2 washers. How about a picture?

wrong fuel filter?