Sealing NPT fittings?

#1

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.

PS – this is where carter gets to tell me "I told you so" re his warning that the accusump may be more trouble than it’s worth. :blush:

Post edited by: sharkd, at: 2006/02/13 14:23

#2

sharkd wrote:

[quote]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 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.

PS – this is where carter gets to tell me "I told you so" re his warning that the accusump may be more trouble than it’s worth. :blush:[/quote]

You have to tighten the hell out of tapered pipe threads. That’s just the nature of them. Using teflon tape or paste are correct. How bad is the leak? If its a slow ooze, then you are probably a half to full turn away.

#3

According to Dan (my mechanic – not referring to myself in the 3rd person), some are a slow ooze (the fitting is wet to the touch) and others are more obvious leaks. He says that he’s tightened them as far as they will go – on the bench.

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.

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

#4

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

#5

Dan,
Get a hardening type of sealant. I use some sort of brown permatex goo on my fuel rail NPT to AN fittings on the 911 (and also on my old Jeep). You HAVE to let it dry a day or two before using. NPT sucks in a vahicle. You’ll learn to appreciate any design that uses AN or at least some sort of crush ring from here on out.

An alternative is to weld (or braze) the AN adapters on, but harder to do at this stage since the casting has had oil introduced.

SMD

#6

sharkd wrote:

[quote]According to Dan (my mechanic – not referring to myself in the 3rd person), some are a slow ooze (the fitting is wet to the touch) and others are more obvious leaks. He says that he’s tightened them as far as they will go – on the bench.

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.

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

How is he counterholding the accusump on the bench? When I installed mine, I used the strap clamp mounts which hold the accusump pretty tight so I could crank hard on the electric valve and the brass hex tube for the pressure switch.

#7

I’m not quite sure – I’ve asked Dan to look at the threads and see if there’s anything he’s missed or if anything clicks in his mind.

#8

Update… it’s gets weirder: Both Dan Martin 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.

:blink:

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

#9

sharkd wrote:

[quote]Update… it’s gets weirder: Both Dan Martin 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.

:blink:

I called Canton and they insist that their fittings are NPT. :huh:[/quote]

That sounds highly unlikely. Maybe one of the parts accidentally got made with straight pipe thread, but all of them? I’m pretty sure those two components aren’t even made by the same company. Easy way to find out is to go buy some NPS male threaded widget at the hardware store. If it threads into the female part like an NPT, then you know its not NPS.

#10

I know, I can’t figure it out, either… I think I’m just going to have to send the Canton mfd parts and the connecting fittings to Canton and see what they make of it.

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

All of the NPT to AN fittings are Earl’s & Aeroquip; all of the NPT to NPT are Earl’s and Summit and all of the AN-hose to AN fittings are Aeroquip (but they’re not leaking).

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.

Post edited by: sharkd, at: 2006/02/14 12:01

#11

sharkd wrote:

[quote]I know, I can’t figure it out, either… I think I’m just going to have to send the Canton mfd parts and the connecting fittings to Canton and see what they make of it.

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

All of the NPT to AN fittings are Earl’s & Aeroquip; all of the NPT to NPT are Earl’s and Summit and all of the AN-hose to AN fittings are Aeroquip (but they’re not leaking).

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.<br><br>Post edited by: sharkd, at: 2006/02/14 12:01[/quote]

Do you know how many of the NPT threads are still showing after they are fully tightened?

#12

I don’t – I’m not hands-on the car right now… It’s at a shop in Gaithersburg. (I hate living in an apartment building.)