You are probably right about the NPT not needing any sealer or tape. The coatings they put on hydraulic lines seldom rusts very badly and I've never seen them be extremely resistant to coming apart. I did feel that the couplers on these hoses, even with obvious tape and dope on them came apart extremely hard! They were torqued well beyond what I would consider necessary. Regardless, I've always used tape myself. I just asked because there have been improvements in just about everything since I did this over a decade ago when working on hydraulics occasionally (on construction equipment when lines burst).
I haven't worked on any of my tractors hydraulic lines (even though I should have) for at least the last decade. If it still works, deal with it...hahaha! Bad ideology I guess. But 'dealing' at this point was getting to be a major PITA since the levers were pretty well stuck tight I found out. Had I done a little recon mission I might not have had to buy those other valves. I was under the impression the sticking was due to messed up set of valve guts. I was afraid the spools had scored the bore too. I'll be taking those apart soon to see if in fact they are bad.
So, the tractor is all together now and it works, no leaks. Valves move like a warm knife through soft butter, the detentes work as far as I can feel so far, at least on the one I tested. The other feels like they will work, it pressurizes both hose and pushes back on my hand as soon as they are, which is instantly.
I believe I have a problem with one cylinder hose nipple now. The cylinder only cycles one way, switch leads and it cycles the other way when pushing valve lever in the opposite direction. (the valve worked it in both directions of the valve lever, but the one hose prevented the opposite action from happening) It could be I didn't have a good solid grip on the one hose when I was pushing them together, I was dripping with sweat and my hands were greasy and that hose was messier than the other. The couplers felt locked but maybe they weren't on that one hose. (I put new o-rings in all four of the two-way couplings yesterday) But it stayed with the same hose as I moved them. I'm going to hot water wash them when the weather cools some. Get all that old built up hydraulic gunk off the back of the tractor. I haven't mounted the female two-way couplers back onto the tractor yet.
The cylinder nipples are old and they weep too much for my liking, they are the ball valve type, I'm just going to be swapping them for new ones of the same type for now since I have a couple of new ones on hand (today maybe?). If that doesn't fix it then the valve is likely bad (doesn't appear to be bad) and I'll have to remove it again. Of course it's the innermost valve....I haven't tested the outer valve yet, the flying critters chased me inside last evening.
Regardless, I'm not going to do much outside today, it's too hot for my fat self to be out there working in the sun for too long today. I'll run out and do some small stuff for short periods, test that other valve, maybe change those nipples. Easy work.
The heat beat me up yesterday and the day before, it chewed on my brain a little, and spit me out! Today we have warnings. Even higher temps in the 90's and the humidity stays about the same. I used to work 10 hour days in this weather, but age and weight gain has taken it's toll. I like the cold much more than the hot!