G5200 (D600) drain cock valve thread pitch

[dlundblad]

I didn't find a thing online about this so I figured it was worth posting up in more detail. Mine ended up snapping off from the block when I tried removing it during a coolant change.. So lesson learned, use a drill bit, long pick etc. before resorting to removal.

P/n is 15841-73020. About $9 for the Kubota part.
Thread pitch is 1/4"-18 NPT.

This should apply to any G3200 to the G6200 as well as the next generation G1800, 1900 etc. Hope this helps someone.

 

[Steve Corgan]

I wish I would have seen your post before breaking my drain cock off while attempting to remove it. I have the new part now, but I'm confused about the thread size. I want to have the tap on hand before trying to get the piece out of the block. I saw a post on here somewhere that said the thread is 1/4" x 18 BSPT and not NPT. I'd never heard of British Standard Pipe Thread before. Now, I can't find that post so I'm unsure. Can you clear up my confusion? Will the NPT tap work? Thanks, Steve

 

[HamBandit]

I can confirm that you can chase the threads with 1/4"-18 NPT tap.

Both the 1/4 NPT brass plug I bought and the OEM Petcock would fit

 

[lmichael]

So if the drain cock is NPT threads on this I'll assume same for the D728 in my G2160? And if so any possibility temp sending unit is NPT?

 

[HamBandit]

I don't think the threads are NPT, they are BSP

From my understanding, its just the thread angle that is slightly different, so you may get away with whatever NPT changes you want to make

 

[Hugo Habicht]

NPT is 18tpi whereas BSP is 19tpi. Otherwise the diameters etc. are almost identical.

I don't remember 100% what tap I used when making a new drain valve, reusing the inner part.

 

[TheOldHokie]

NPT is 18tpi whereas BSP is 19tpi. Otherwise the diameters etc. are almost identical.

I don't remember 100% what tap I used when making a new drain valve, reusing the inner part.

Not only is thread pirch different the flank angle on BSP is 55 degrees vs 60 degrees for NPT. They DO NOT INTERCHANGE.

The diameters are close but a $15 caliper from HF will easily differentiate BSP from NPT

Dan

 

[Hugo Habicht]

Not only is thread pirch different the flank angle on BSP is 55 degrees vs 60 degrees for NPT. They DO NOT INTERCHANGE.

The diameters are close but a $15 caliper from HF will easily differentiate BSP from NPT

Fair enough. But going through about 7 turns (as on the picture above) with a tap you would not notice that something does not match.

And so far I only found metric or BSP threads on my tractor. I admit, does not prove anything.

 

[HamBandit]

Are you sure they don't interchange? I could thread the OEM Coolant drain into the threads I tapped

 

[TheOldHokie]

Fair enough. But going through about 7 turns (as on the picture above) with a tap you would not notice that something does not match.

And so far I only found metric or BSP threads on my tractor. I admit, does not prove anything.

You would not notice but the threads would be imperfect. You can even jam some sizes together right out of the box but the pitch diameters, flank angjes, and in some sizes thread pitch do not match and the threads do not seal correctly. In other words THEY DO NOT INTERCHANGE.

I would expect BSP not NPT on a Kubota diesel engine. Plenty of examples of that in the imported (NA) automotive world.

Dan