BSP thread expert help please?

[Vintage Veloce]

On my truck, it's possible to submerge the rear axle when off-roading. To prevent water entering the differential, it is recommended to replace the rear differential breather with a barbed fitting and to run a hose to a point higher on the truck.
So I took the rear differential breather out of my truck:

This is a G 1/8 BSPP fitting. The threads are parallel, not conical. There was no seal on the threaded connection, which makes sense as the cap is open to the air anyhow.

Now, I have not been able to find a barbed BSPP fitting with parallel threads.
But, I was able to find a "6mm barb x G 1/8 BSP male pipe adapter" that clearly has conical threads:

Now this thread right into the hole without problem. But it's threads are obviously tapered, maybe it is an "R" tapered thread and not actually a "G" parallel thread?

I have heard that it is OK to use the tapered threads in a parallel thread hole (is this true?) and it does fit. But my real concern, is this water tight? If I get stuck in a stream crossing, is this in danger of leaking water into the differential? How do I best seal this joint?
(Note I am hesitant to use pipe tape or goop on these threads, as they are fairly inaccessible and I do not want to have stuff fall into the diff, if I remove/change this fitting.)


I could probably get a parallel BSP (BSPP) fitting, but my understanding is that requires a gasket to seal, and I doubt the surface of the diff will allow easy gasket sealing.

What say the experts? What should I do here to make a watertight seal?

 

[TurnipTruck]

Wipe some Teflon paste or antiseize on the threads and tighten it to snug-plus.
What will you do on the upper end of the hose? Tiny lawnmower fuel filter?

 

[Vintage Veloce]

Wipe some Teflon paste or antiseize on the threads and tighten it to snug-plus.
What will you do on the upper end of the hose? Tiny lawnmower fuel filter?

Tiny air filter tucked in behind the tail light. It's easy to run a hose from there to the underside of the truck.
teflon paste... this is advised for BSPP tapered thread to the parallel thread hole?

 

[TurnipTruck]

There is some thought that the actual seal in a tapered pipe thread is the metal-to-metal interference, and whatever lube applied just reduces the torque necessary to attain that seal. In your case, wherever the torque increases while tightening the tapered fitting into the parallel hole is where the interference fit begins and the threads begin microscopically conforming to each other.

 

[ducatithunder]

BSPT is a british taper similar to NPT but not quite. I have see many people thread them into each other over the years. BSPP is a parallel pitch which requires a gasket seal and usually is fully threaded with a gutter or landing at the top. I dont see that in your fitting original fitting. The fitting you got looks like a BSPT to me if its not NPT. If you could get the BSPP fitting I would hammer a flat or use a file to make a nice flat landing for a copper washer to seal. Shouldnt take much of a flat surface to get a good seal.

If your happy with your current fitting and got it snug, I would just take some Loctite 545 and thread it back in for a weather tight seal.

 

[nadogail]

I had a somewhat similar problem and the local Parker hydraulic shop was able to connect my metric pneumatic cylinder to US sized hose.

 

[PCustoms]

Xterra?


There's a whole thread out there on newex.....

 

[Vintage Veloce]

Xterra?


There's a whole thread out there on newex.....

Yes, but not really anything there on properly sealing the joint. Frankly, there are some guys just mashing the wrong threads (bsp to npt) together.

 

[PCustoms]

Yes, but not really anything there on properly sealing the joint. Frankly, there are some guys just mashing the wrong threads (bsp to npt) together.

There should be a thread calling out the correct PN that fits and adapts to a hose.....

I sold my '11 pro4x last year, 10 new England winters had been hard on it, parts were starting to fall off and needed tires. Had visions of laying in the slush fixing something, remote start and heated seats was a nice upgrade!

I think you can tear the dumb vent off the factory fitting and attach hose directly to that, but I can't remember what I did. Diff didn't leak....

 

[firebirdparts]

I gotta tell you, the differential is almost indestructible. Your fear of Teflon tape or sealant falling in is not really necessary.

Any sort of “stuff” is going to seal it. There’s no driving force for that to ever leak. It takes about 30 inches of water just to make 1 psi pressure on it.

 

[ycgoat]

I would try to Braze 2 fittings together and use an O-ring to seal the straight thread connection

 

[pancho400cid]

You could buy a G/18 (1/8 BSPP) male x 1/8 NPT female adapter.

G1/8 x 1/8 NPT adapter

But technically BSPP threads must seal by one of three methods:

A - Gasket or O-ring under the fitting hex/body
B - Gasket or O-ring at the bottom of the male threads
C - Inverted flare at the bottom of the threads

I don't see "A" working since the axle tube is round with no apparent counter-bore. So you'd need to check to see if "B" or "C" would work. They won't if the hole is threaded all the way through.

And of course there is always JB Welding your tapered fitting into the hole.

 

[PCustoms]

There's a Nissan pn that is a perfect fit....

 

[Vintage Veloce]

If your happy with your current fitting and got it snug, I would just take some Loctite 545 and thread it back in for a weather tight seal.

This is looking like a sensible idea...

 

[BillK]

McMaster Carr https://www.mcmaster.com/4406T893/

 

[bmxdukie]

I'd go bsp to jicM adapter. Then jicF to barb it there is room. If not, go bsp to jicM on a 90deg.

 

[charbar]

In my opinion your way over thinking something that's fairly non critical. It looks like the barbed fitting you have fits 'good enough' to just put some sealant on (literally about anything will work for what you are trying to do) and call it a day.

 

[Mick56]

Pop the cap off your original breather, there may be enough of a stub to put the breather hose on with a clamp.

 

[Vintage Veloce]

OK, more research shows lots of sources saying that using a:
BSPT (tapered) male into BSPP (parallel) female
is acceptable, maybe even preferred usage.

(source:https://www.adaptall.com/info-tutorials/sealing-methods.php)

So the only question is what to use as a sealant, if anything.
I'm tempted by the Loctite 545

(yes this is more thought maybe than necessary... but If I am replacing this open breather with a hose, I certainly want to feel certain it will work as I intend.)

 

[andyvh1959]

BSPP and BSPT use the same thread pitch per size, one is tapered and one is parallel (straight). BSP thread is close to NPT but with a different thread pitch with the exception of few sizes that have the same thread pitch. However BSP and NPT also have different thread pressure angles. BSPP is very common on lower pressure applications, especially on large engines for the drain ports, cooling systems, etc. BSP is commonly detailed on the fitting with a G stamped on the fitting body.

NPT vs. BSPT Pipe FAQs - Advanced Technology Products