Fuel tank issues

Dave Wave

Member
So I replaced the fuel tank on my NAA with this:

http://www.ebay.com/itm/NAA9002E-Ford-New-Holland-Tractor-Gas-Fuel-Tank-600-700-Series-701-NAA-Jubilee-/400478462840?pt=BI_Heavy_Equipment_Parts&hash=item5d3e606378

This tank is supposed to fit the NAA tractors and some of the later ones as well like the 600 and 700.

I guess ford moved the shutoff valve from the side to the center later on. This tank came with a bolt to plug the unused hole.

My issue is that my stock NAA shut off valve will not thread into the tank. It binds like it the wrong pitch thread.

Does anybody know if the later ford shutoff valves are a different pitch than the fine pitch ones on the NAA? The shutoff valve the seller sent for the tank seems to be a fine pitch valve, just like the original on the tractor.

Anybody have any insight?

Thanks!

-Dave
 
You need a screw pitch gauge.If the plug that came with the tank is a different pitch from your sediment bowl the gauge will prove it.The tank could be metric.
 
So I poked around a bit with my pitch gauge, and it seems that the tank is tapped 5/8-18 (fine), which matches the original shutoff valve.

That leads me to believe the issue is probably a burr of some-sort. Not wanting to drop $20 on a tap to chase one thread, Any tips or tricks to cleaning up the thread?

Thanks,

Dave
 

5/8-18 (fine), which matches the original shutoff valve.

That does not calculate to me... Are they not spouse to B 3/8 pipe thread...
 
I do not know. I took the seller at their word. A pipe thread would seem like the right choice. I'll check the shutoff valve and report back. Thanks,

-Dave
 
(quoted from post at 19:23:47 06/28/13) So I poked around a bit with my pitch gauge, and it seems that the tank is tapped 5/8-18 (fine), which matches the original shutoff valve.

That leads me to believe the issue is probably a burr of some-sort. Not wanting to drop $20 on a tap to chase one thread, Any tips or tricks to cleaning up the thread?

Thanks,

Dave

I am more inclined to think your fitting is a 3/8" taper pipe (NPT) thread:[list:5f3a8bfbcd][*:5f3a8bfbcd]18 threads per inch[*:5f3a8bfbcd]Major diameter of .675[*:5f3a8bfbcd]3/4" taper per foot.[/list:u:5f3a8bfbcd]You can start a 5/8-18 UNF bolt in the female pipe fitting but it quickly binds due to the taper. Test fit a $.50 pipe plug and I think you will find it works nicely....

TOH
 

Whut he said his head is loaded for bear when it comes to numbers :D

In the pix it does look like a bolt has been installed in the hole whats up with that I dunno,,, the seller has had issues by his wright up and its misleading...

Get a pipe plug lube it with pipe dope and use it to clean up the threads before you mess up your original.. Chines pipe threads are a issue but I have had luck with pipe dope used on the threads to lube and straight'n them up...

What I have ran into on these threads...

have found good old pipe dope to work the best on those ell fitting fittings...

If it does not feel good going together its not gonna seal,,, if it squeaks and squats its not gonna seal,,, If it appears to not engage enough its not gonna seal,,, I have found it best to pre-assemble till it feels right with good old pipe dope...

The treads are so ell fitting they need lubrication that's my take on it...

BTW use a brass are a non coated test plug...
 
(quoted from post at 07:37:24 06/29/13)
Whut he said his head is loaded for bear when it comes to numbers :D

In the pix it does look like a bolt has been installed in the hole whats up with that I dunno,,, the seller has had issues by his wright up and its misleading...

Get a pipe plug lube it with pipe dope and use it to clean up the threads before you mess up your original.. Chines pipe threads are a issue but I have had luck with pipe dope used on the threads to lube and straight'n them up...

What I have ran into on these threads...

have found good old pipe dope to work the best on those ell fitting fittings...

If it does not feel good going together its not gonna seal,,, if it squeaks and squats its not gonna seal,,, If it appears to not engage enough its not gonna seal,,, I have found it best to pre-assemble till it feels right with good old pipe dope...

The treads are so ell fitting they need lubrication that's my take on it...

BTW use a brass are a non coated test plug...

Well I just read his write-up which is what I should have done BEFORE I posted my first response. His write-up is perfectly clear:

"[i:2c935cd527]This tank has [color=red:2c935cd527]straight threads[/color:2c935cd527] in the sediment bowl hole. If your old sediment bowl has diferent threads we recomenned ebay item number 221081754982 as a replacement bowl. Our replacement bowl has [color=red:2c935cd527]tapered threads made to seal in the straight cut threads [/color:2c935cd527] on this tank[/i:2c935cd527]."

What he doesn't say is exactly what thread form is used in the tank fitting. Based on the eBay description they sound like National Pipe Straight Fuel (NPSF) or National Standard Straight Coupling (NPSC) which are designed to form a pressure tight seal when mated with NPT or NPTF male fittings. If combining an NPSC with NPT(F) type male fitting a sutable thread sealant must be used to obtain a pressure tight seal. In all straight/taper combinations the tapered male fitting is typically made from a soft /ductile material (e.g. brass) that will compress and conform to the mating straight threads. A 5/8-18 UNF male fitting will not make a reliable mechanical or pressure tight joint when joined with a NPSF/NPSC coupling - it will be loose and leak.

But wait - there's more!!!

All told there are at least 10 different American National Standard pipe thread forms (ANSI/ASME B1.20.1) and a thread pitch gage will only get you a partial ID. The most common form is probably the National Taper Pipe thread (NPT) found in the plumbing section of your hardware store which requires a thread sealant to effect a pressure tight joint. It is often confused/interchanged with the National Standard Dryseal Pipe thread which does not require a sealant and comes in 4 different variants some of which are straight thread and some of which are taper thread (NPTF, NPSF, PTF, NPSI). The many different pipe thread variants are designed for different applications, have subtle differences in their geometries, substantially different mechanical and pressure sealing requirements, and don't all play well together. You really need to know exactly what you have and what it's designed to mate with when making up new connections.

TOH
 
(quoted from post at 18:38:12 06/29/13)
(quoted from post at 07:37:24 06/29/13)
Whut he said his head is loaded for bear when it comes to numbers :D

In the pix it does look like a bolt has been installed in the hole whats up with that I dunno,,, the seller has had issues by his wright up and its misleading...

Get a pipe plug lube it with pipe dope and use it to clean up the threads before you mess up your original.. Chines pipe threads are a issue but I have had luck with pipe dope used on the threads to lube and straight'n them up...

What I have ran into on these threads...

have found good old pipe dope to work the best on those ell fitting fittings...

If it does not feel good going together its not gonna seal,,, if it squeaks and squats its not gonna seal,,, If it appears to not engage enough its not gonna seal,,, I have found it best to pre-assemble till it feels right with good old pipe dope...

The treads are so ell fitting they need lubrication that's my take on it...

BTW use a brass are a non coated test plug...

Well I just read his write-up which is what I should have done BEFORE I posted my first response. His write-up is perfectly clear:

"[i:2042a046ff]This tank has [color=red:2042a046ff]straight threads[/color:2042a046ff] in the sediment bowl hole. If your old sediment bowl has diferent threads we recomenned ebay item number 221081754982 as a replacement bowl. Our replacement bowl has [color=red:2042a046ff]tapered threads made to seal in the straight cut threads [/color:2042a046ff] on this tank[/i:2042a046ff]."

What he doesn't say is exactly what thread form is used in the tank fitting. Based on the eBay description they sound like National Pipe Straight Fuel (NPSF) or National Standard Straight Coupling (NPSC) which are designed to form a pressure tight seal when mated with NPT or NPTF male fittings. If combining an NPSC with NPT(F) type male fitting a sutable thread sealant must be used to obtain a pressure tight seal. In all straight/taper combinations the tapered male fitting is typically made from a soft /ductile material (e.g. brass) that will compress and conform to the mating straight threads. A 5/8-18 UNF male fitting will not make a reliable mechanical or pressure tight joint when joined with a NPSF/NPSC coupling - it will be loose and leak.

But wait - there's more!!!

All told there are at least 10 different American National Standard pipe thread forms (ANSI/ASME B1.20.1) and a thread pitch gage will only get you a partial ID. The most common form is probably the National Taper Pipe thread (NPT) found in the plumbing section of your hardware store which requires a thread sealant to effect a pressure tight joint. It is often confused/interchanged with the National Standard Dryseal Pipe thread which does not require a sealant and comes in 4 different variants some of which are straight thread and some of which are taper thread (NPTF, NPSF, PTF, NPSI). The many different pipe thread variants are designed for different applications, have subtle differences in their geometries, substantially different mechanical and pressure sealing requirements, and don't all play well together. You really need to know exactly what you have and what it's designed to mate with when making up new connections.

TOH

I assumed his replacement bowl was the standard OEM type I see now its not thanks for clearing that up...
 
Well I found a 3/8 NPT tap. I chased it into the hole by hand. It went in a couple turns then bound up. I did not force it.

I measured my stock shutoff valve (exactly the same as the one the seller sent). It is tapered, and runs from .654 to .6735.

So I guess the options at this point would be to force the tap and try and rethread the existing threads to 3/8 ntp, or trying to find a 3/8 -18 tap and chasing threads to see if that will get it started.

Anybody care to comment?

Thanks,

-Dave
 
(quoted from post at 14:48:12 06/29/13) Assuming the tank is threaded 3/8 -18 and the shutoff valve is 3/8 NPT - would that combination work?

-Dave

No - it wouldn't even start into the hole. Do as the seller says - the straight thread that is in the tank is designed to seal with a properly sized taper pipe thread. If you bought the sediment bowl fitting he referenced in the gas tank listing (item number 221081754982) it should work properly. Put a little pipe thread sealant or a wrap of teflon tape on the male thread before you install it. It should go in almost two turns until it is hand tight. Then give it another turn with a wrench until it is properly oriented. Done.

TOH
 
I did get the bowl from him. I will put some sealant on it and give another go. I guess we can add Turkey to the list of the land-of-not-quite-right.

Thanks again for all the help!

-Dave
 
(quoted from post at 16:54:15 06/29/13) I did get the bowl from him. I will put some sealant on it and give another go. I guess we can add Turkey to the list of the land-of-not-quite-right.

Thanks again for all the help!

-Dave

Well I found a 3/8 NPT tap. I chased it into the hole by hand. It went in a couple turns then bound up. I did not force it.
-Dave

You are operating under a bunch of misconceptions and confusing a bunch of different thread specs . If the tank is tapped for 3/8 STRAIGHT pipe threads as described by the seller (NPSC or NPSF) a 3/8 NPT pipe thread will start and "bind" after a turn or two just as you describe.

[b:f51472e1ac][u:f51472e1ac]THIS IS HOW IT IS SUPPOSED TO WORK[/u:f51472e1ac][/b:f51472e1ac].

It is not almost right - it is dead on right and exactly how the ANSI pipe thread specification specifies it should work. The interference between the straight threads on the tank and the taper threads on the tap is what gives you a pressure tight seal. If you run the tap in deeper you will ruin the NPSC/NPST threads in the tank and potentially compromise the seal. Leave it alone!!!

I measured my stock shutoff valve (exactly the same as the one the seller sent). It is tapered, and runs from .654 to .6735.
-Dave

Your measurements on the old sediment bowl are consistent with 3/8" NPT threads just as Hobo told you. It should screw into the new tank just like the tap. If it does put some sealant on the threads, run it in hand tight, and then use a wrench to tighten it 1 -2 turns more just until it is at the correct orientation.

TOH
 

Well I lubed it up with some dope and got it started. It bound up at about 1/4 of a turn. Thinking about what TOH and the others said, I put the wrench on it and started turning it in. Much to my surprise, it did not strip out. It made it about 1 1/2 turns and was getting pretty stiff, so I left it there. I added some gas, and so far no leaks.

So far, so good.

This is one strange thread setup. It felt exactly like the threads were crossed.

Thanks for all the help and explanations!

-Dave
 

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