Hydraulic block-off plate plug

[esbrian]

When I purchased my 850, the plug in the hydraulic block-off plate on the hydraulic top cover had been removed and replaced with a street elbow fitting connected to a hydraulic hose running to the rear of the tractor which, as I understand it, could have been used to operate a single-acting cylinder by chaining the lift arms down.

In the process of installing an HV-5902 adapter plate, I removed the hose from the block-off plate. My parts manual describes the plug (part 87652-S) as "plug - 3/8-18 pipe." I have installed a 3/8 MPT pipe plug in this port and am getting a little leakage when lifting a load on the 3-point lift arms. I can tighten it more, but before wrenching on it I wanted to make sure I am using the correct thread and not damaging the port in the block-off plate. At Steiner, the block-off plate threaded port is described as "9/16" - 18 NF."

Is a 3/8" pipe plug correct for this application?

 

[Bern]

The hole can't be 9/16 because a 3/8 NPT plug wont even start in that hole. Did you use pipe dope or thread tape on the threads?

 

[esbrian]

(quoted from post at 17:21:06 12/29/21) The hole can't be 9/16 because a 3/8 NPT plug wont even start in that hole. Did you use pipe dope or thread tape on the threads?

Bern, I used PTFE thread sealant paste.

 

[Bern]

Sounds like you need to tighten the plug more then.

 

[Jim.ME]

(quoted from post at 19:36:10 12/29/21) Sounds like you need to tighten the plug more then.

That does not sound like it uses a pipe plug to me. 9/16-18 NF is the thread designation for 3/8" (or -06 size) O-ring boss fittings. It is not the same as 1/4 NPT, which has a diameter of about .566" and an 18 TPI pitch and is tapered. 3/8 O-ring boss thread is 9/16-18 straight just like a 9/16" fine thread bolt. Looking at the picture on their website, it very much appears to have the chamfered seat for an O-ring boss fitting. You may get a pipe plug to seal or you may ruin the threads for the right fitting.

This post was edited by Jim.ME on 12/29/2021 at 04:21 pm.

 

[Bern]

Jim, I think you're on to something here. I bet the OP is working with a 1/4 NPT plug rather than the 3/8 he thinks it is. I just went out to my garage and threaded a 1/4 NPT plug into a 9/16 ORB hole. It's an extremely sloppy fit, but it does thread in easily and would give a person a sense of seating if it was tightened enough. It would also explain why it leaks even with thread sealant on it.

 

[esbrian]

It is definitely a 3/8 plug i have in there, purchased it immediately after reviewing the parts manual to confirm what i was shopping for. Its a snug fit.

To me, 3/8 pipe means npt. Is it possible that ford changed the part at some point and i have a non-original plate?

The fact that the top of the boss where it threads into is ground flat is suspicious, though - why would a pipe plug need a ground boss? My block off plate is not cast, but the steiner part is. I will pull it and see if there is a chamfer for an o ring. If so, hopefully i havent fouled the threads to the point where it wont hold an orb plug.

Brian

 

[Jim.ME]

The original may have been 3/8 NPT, but the new plate is aftermarket and just like loader valves and a lot of other hydraulic items they are being built with/for the newer style fittings. It would have been good if they advertised it as 3/8 O-ring boss, or even included a proper plug with it.

 

[Jim.ME]

The description for the HV-5902 in the Y Store listing clearly says it has 3/4 - 16 O-ring boss ports. So a 3/8 NPT plug could be threaded into those ports.

So if you are installing a (TISCO) HV-5902 kit from somewhere, don't count on the parts book to be correct for aftermarket parts thread sizes or fitting types.

You have mentioned the block off plate on the tractor, block off plate from Steiner and the HV-5902. If you are trying to plug the plate that was on the tractor (with a hose in the port), what was the thread of the hose fitting. Get a plug that matches those threads if it wasn't leaking.

This post was edited by Jim.ME on 12/29/2021 at 05:49 pm.

 

[esbrian]

Jim, i have installed a 5902, but the port i am referring to is in the block off plate that was on the top cover before installing the plate. The tisco instructions are clear on the 5902 ports. I am trying to replug the port on the blockoff plate that was present before 5902 install. This is the port that the previous owner had installed a 3/8 npt street elbow in to operate an SA cylinder. Now that i have installed the 5902, i am just trying to plug the port in the factory blockoff plate.

Between the parts manual describing it as 3/8 pipe plug and the fact that the 3/8 npt elbow never leaked, i assumed that a 3/8 pipe plug was appropriate. I have tightened the plug to the point where i would expect a good seal, but given that i do not seem to have a good seal i am questioning the parts manual and my installation of an npt plug as opposed to an orb plug.

 

[esbrian]

Sorry if i sound cranky, gentlemen! I had family drama going on in the background and put all my patience toward that front

 

[Jim.ME]

So the reference to the thread in the port of the Steiner plate really is not in play here. If the elbow in the old plate was 3/8 NPT you need a 3/8 NPT plug. The elbow and plug may be slightly different in taper,so the new plug going into the threads the elbow was in doesn't fit as well. We are back to tighten it more. If needed you can use tape, along with the pipe dope, just keep the tape above the first thread or two so as not to get tape into the system.

 

[JMOR]

How about............if the el didn't leak, put it back and plug the el output?

 

[Sean in PA]

It's been several years since I installed the HV5902 on my 4000, but I am pretty sure that all of the ports are O-Ring Boss (ORB) fittings.

 

[esbrian]

(quoted from post at 14:52:25 12/30/21) It's been several years since I installed the HV5902 on my 4000, but I am pretty sure that all of the ports are O-Ring Boss (ORB) fittings.

I think I overexplained, as my father does, and his father before him...

the HV 5902 really has nothing to do with this issue aside from the fact that its installation is what gave me occasion to remove the old hydraulic hose and elbow.

This issue is strictly with the plug in the block-off plate that sits on top of the hydraulic top cover on a stock tractor. Based on the responses so far, I will remove the plug, clean it up, reapply paste and possibly tape, and try to tighten it to the point where it no longer leaks. As several posters have pointed out, if the pipe elbow that was in there before didn't leak, a properly-installed pipe plug should do the job.

Thanks everybody, will report back when I am leak-free or have broken my block-off plate

 

[Sean in PA]

(quoted from post at 21:34:21 12/30/21)

(quoted from post at 14:52:25 12/30/21) It's been several years since I installed the HV5902 on my 4000, but I am pretty sure that all of the ports are O-Ring Boss (ORB) fittings.

I think I overexplained, as my father does, and his father before him...

the HV 5902 really has nothing to do with this issue aside from the fact that its installation is what gave me occasion to remove the old hydraulic hose and elbow.

This issue is strictly with the plug in the block-off plate that sits on top of the hydraulic top cover on a stock tractor. Based on the responses so far, I will remove the plug, clean it up, reapply paste and possibly tape, and try to tighten it to the point where it no longer leaks. As several posters have pointed out, if the pipe elbow that was in there before didn't leak, a properly-installed pipe plug should do the job.

Thanks everybody, will report back when I am leak-free or have broken my block-off plate

Yes, the parts drawings say that is a 3/8" - 18 pipe plug. If that's not sealing I would try some pipe dope or teflon tape. Just make sure that you don't get any pieces of teflon tape inside the hydraulics system. When sealing NPT fittings for hydraulics systems I usually use the yellow teflon tape that's actually designed for natural gas fittings because it's thicker than the white stuff and seals the higher pressures better.

 

[esbrian]

(quoted from post at 12:09:20 12/30/21) How about............if the el didn't leak, put it back and plug the el output?

jmor, that is a potentially legit solution, but I'm pretty sure the elbow would make me angry every time I looked at it. I need a solution that is both leak-free AND makes me nod in satisfaction when I see it, instead of shaking my head in shame.