I have 1/4" NPT connections on a Racor fuel/water separator. The threaded in hose barbs leak

Can anyone recommend a pipe thread sealant that will work with diesel on this type of application? Ideally, one that can be put back in service fairly quickly.

BTW, Teflon tape did not work.

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

I use the paste with good results, usually just loctite thread paste or whatever.

Its not an actuwl crack in the filter head is it? The cast aluminum can be fragile especially when cranked down on

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Which Racor? Are you SURE it's NPT? Many of them are ORB.

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617 swapped Toyota Pickup, 22-24 MPG, 50k miles on swap

Not sure for your application but...
super-glue. I've used it on leaking diesel injector bodies. Made the injector harder to take apart later but it worked.

Sprayed with brake cleaner, than did several shots of super glue to fill the threads.

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1985 300TD 1981 Scirocco 1.6D conv 1986 Golf 1.6D 2003 Golf TDI

Permeated Form a gasket 3 is what you need.

If you mean Permatex Form-a-Gasket #3, I believe that is the one called Aviation. I have that and have used it on threaded connections. But it didn't work well for me. But there was a reason!

Firstly, the filter appeared good, but we bought a complete new one anyway! Installed it and it too leaked! They don't come with hose barbs, so we used the old ones.

What we finally found, was that although the filters were threaded for 1/4" NPT, the hose barbs readily available at auto stores don't have a tapered thread - (it's probably -4AN) - they screwed in, but thread match was not good.

We found NPT hose barb fittings at Home Depot (plumbing dept) Installed those using Permatex High Temperature thread sealant (also plumbing dept!) - it specifies that it is good for diesel fluid (as well as most other fluids!)

Thanks for input. No leaks so far!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5

NPT threads always need a bit of sealant.

No.

Npt threads are tapered, and SHOULD only need an anti-galling lubricant for the threads, and proper tightening.

If sealant, or hardening material is needed, something is done improperly.

Incorrect tightening, incorrect fittings, or damaged fittings.

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John HAUL AWAY, OR CRUSHED CARS!!! HELP ME keep the cars out of the crusher! A/C Thread
"as I ride with my a/c on... I have fond memories of sweaty oily saturdays and spewing R12 into the air. THANKS for all you do!

My drivers:
1987 190D 2.5Turbo
1987 190D 2.5Turbo
1987 190D 2.5-5SPEED!!!

1987 300TD
1987 300TD
1994GMC 2500 6.5Turbo truck... I had to put the ladder somewhere!

You probably work with many different types of fittings in your A/C business, so should know.

However, I can't imagine getting away without Teflon tape or a plumbing sealant on my home's lake water system when using standard plumbing fittings!

The fuel filter we are using says to use a sealant on the threads. Just not which one! But does say not use Teflon tape because it could end up in the diesel HP pump or injectors.

After using the Permatex High Temperature thread sealant on new filter and npt hose barbs, leak has gone. But mainly because we now have properly matching threads!

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Graham
85 300D,72 350SL, 98 E320, Outback 2.5