Sealing NPT fittings?

[sharkd]

My mechanic and I are having a bear of a time trying to plug leaks on my newly-installed Accusump. The AN fittings on the hoses are sealing fine, but the NPT fittings between the valves and input adapters and the hoses are not.

He's tried the teflon tape and permatex teflon pipe thread paste (both, independently and together) to no avail.

Does anyone have any advice on what to try?

All of the fittings are quality parts, manufactured by Canton, Aeroquip and Earl's.

[SchnellerVert]

Teflon tape is all you should need.

[sharkd]

It should be, but it's not...

The leaks are coming through the NPT threads on the (M) NPT-to-AN (M) adapter fittings on the Remote Oil Filter Mount and the remote oil filter adapter, as well as the (m) NPT-to-NPT (m) fitting that connects the accusump to the electric valve fitting. (The only NPT that isn't leaking is the 90° elbow M-to-F directly out of the accusump.

The AN-to-AN connections are holding tight.

The fittings are being tightened (on the bench) to the point where they will no longer turn.

Here is a PDF of the plumbing diagram, and a picture of a similarly installed system (without the remote oil filter mount).

[Beej '86 325es]

you're not using a tapered thread male with a non-tapered thread female fitting are you?

[sharkd]

The interior of the female fittings are tapered at the end of the NPT threads; the male NPT all look like the blue aluminum fitting seen in this photo from Canton's website:


Here's an example picture of the Earl's 1/2 NPT to AN-10 that I purchased from Summit Racing:

[sharkd]

I'm juggling a bunch of threads going on a couple of boards... if you're curious about what others have said:

http://nccbmwcca.org/forum/showthread.php?p=11839

http://bimmerforums.com/forum/showthread.php?p=5904486

http://www.e30tech.com/forum/viewtopic.php?p=215588

http://spece30.northamericanbavarianracing.com/index.php?option=com_simpleboard&Itemid=65&func=view&id=2278&catid=5

[sharkd]

you're not using a tapered thread male with a non-tapered thread female fitting are you?

I think you hit the nail on the head... Both Dan Martin (my mechanic) and Roger of Auto Therapy have looked at the fittings and are firmly of the opinion that the female threads in the pressure valve, remote filter mount and remote filter adapter are not ½" NPT that Canton lists in the specs, but ½" straight pipe.



I called Canton and they insist that their fittings are NPT.

Update: Canton's offered to examine all their parts and the corresponding MPT-MPT and MPT-AN-10 fittings that I purchased.

Unfortunately, it means that I won't have the accusump at VIR on friday and that I won't be able to transfer the race car to NC this weekend, like I'd planned (moving in a few weeks, hopefully).

I still can't see how all the Canton fittings could be mis-manufactured, but three different people who are familiar with these kinds of fittings have looked at the parts and come to the same conclusion.

All of the fittings that are leaking are: this AN-10 to MPT (6 of them) and this MPT to MPT (3 of them).