You can't see much of the thread on the pics, but they look OK and not goobered up. It is so surprizing that the nuts would not come out with out so much effort. Glad you were able to get them out.

BTW, before I can suggest anything, this knucklehead has to think of an idea first

 

From one Knucklehead to another..................threads had some rust developing on them.......glad the new lines come with new nuts, as I would hate to have to clean these up and re-use.

 

I wonder if those lines have not been removed since 1994. That would explain how they are getting fused together.

 

I wonder if those lines have not been removed since 1994. That would explain how they are getting fused together.

 

These lines appear to be original factory lines. I do have a technical question for you regarding these lines:

Mitsubishi, like all proud Japanese makers, strictly use Metric sizes on all nuts/bolts/fittings. These lines used a 17mm wrench to loosen both at the steering box. The replacement lines (not Mitsubishi) are using SAE sizes, and all are different. The larger line (return line) has a 5/8" nut on it, and the smaller line (pressure line) has a darn 11/16" nut on it (I tried a 18mm, but it fits a wee bit loose, while the 11/16 is perfect). These lines are bent to fit only the Montero model, so why in the world does these parts makers use SAE nuts when they should have used 17mm?????

I compared the thread size, and they are the same threads per inch. However, there is a variance between the old lines and the new. For example:

Old Return Line: 10.10mm outside dia on tube
15.5mm Thread size
17 mm nut size

New Return Line: 9.55 Outside dia. on tube
15.75 Thread size
5/8" nut size

I put some anti-seize on the threads and tried to thread the line/nut into the steering box hole.......and it is hard to get started, and then takes way too much torquing (in my opinion) to thread it in. So, after one turn I stopped and backed it out to take measurements. It is a bit larger than the old threads, but the old threads were worn down a bit due to their trip into the steering box, and back out again. Should I just go ahead and force this nut into the steering pump, and hope that I dont end up cross-threading the sucker? You ever have these lines screw in so tight like this?

 

Oh man... What a nightmare. I'm also at a loss for why or how someone would manufacture an aftermarket threaded component for a Japanese vehicle with an SAE nut. I think the variance in O.D. tube diameter is not anything to worry about. What is important is the style/size of the flare on the business end of the pipe and the thread size on the nut that is holding it to the pump or steering box. I honestly do not know if it is possible to have an SAE nut with the metric thread size on it. If you remember, these nuts need to be fully seated in order to seal the flare on the mating surface. When you did your test, and the nut stopped turning in (when you though it was no longer comfortable to continue), did it feel like the hard line was seated on the mating surface or was it still loosey goosey? It its still loose - then the nuts and threads are wrong diameter.

The way I see it, there are two options:
1. call back to wherever you got these lines and see if you can get them exchanged for proper ones.
2. get a right size metric die (based on the old thread size). Mount the new nuts in the vice and carefully run the die down onto the nut to shave off a little bit of the of extra material from the thread channels. I suppose it is possible that when these nuts were made, they die they used was old and worn, so the thread pitch is correct, but it did not form the right depth of the thread.

Check the depth of the new and old nuts from the tip of the flare. How do they compare? Just to be on the safe side - run the old nuts back in and see how many turns it will take to seat the flare fully. If you can't get that many turns from the new pipe/nut - you will not be able to continue.

 

Hunter.......Some close-up shots of the smaller line (High Pressure Line.....I goofed and marked it as Return Line).
The total length of the threads are longer on the new lines as compared to the factory lines (17.4mm vs. 14.7mm). This just means that you cannot over-crank these nuts, or you will destroy the ORing and seat. The old nuts were made to seat flush to the steering gear unit.

You can see that the old treads look worn-down......is that just due to them fitting so tight into the female threads on the steering gear?










The thread dia. on the old worn threads is 13.35mm, and the thread dia. on the new threads is 13.75. So thats half a millimeter larger. Since the old nuts threaded out pretty tight all the way when removing them, do you think this extra .5mm is going to be too tight and cause stripping of the threads? Scarey situation.....If I force them in and ruin the female threads on the steering box, then the steering box is toast.

Yes, the line was "loosey goosey" when I was trying to thread the nut into the steering box hole.....I could pull up/down on the tubing as the nut was turned in a bit (but getting real tight).

You mentioned a way to remove some of the thread thickness on the new nut....using a metric die.....I think I have a set, and will see how that fits. Just like you said, it would seem that if they used SAE nuts, then likely they used SAE thread size, not metric. But when I placed the threads on top of each other, they seem to line up correctly. (I had thought about putting the nut in a vice and using a hand file to take some of the thread thickness off.)

Once again, why in the world do these parts makers change all the specs on these parts.....wrong nut size (17mm vs. 11/16 and 5/8), wrong thread length on nuts, etc. Just a total failure to reproduce a part. The other bad thing is that with Rock Auto, you cannot call and speak to someone......and there is no online discussion/email system.....all you can do is complain by returning the part (and pay all the shipping charges twice if you take a chance and reorder).
Very frustrating indeed.

 

Hunter.....I just measured the dia. sizes of the tip of the tube that fits down into the steering box.
The new tube is slightly larger, but I assume not enough to have issues:

New tube tip dia at the very tip: 7.2mm Old tube tip: 7.1 mm

The "doughnut ring" that pushed down on the ORing is: New tube: 11.63mm Old tube: 11.43mm

So, dont you agree that this is within specs?
Now, the only issue are those darn threads being a bit large, and perhaps not metric.

 

Yes, the tube and o-ring seem to be just the right sizes. Question for you - when you are measuring thread diameter, are you measuring outside the threads or inside the threads (ridges of valleys)? If outside (ridges), then the difference could be from just old thread being chewed up a little. Check inside thread diameter, if they are close, perhaps you are good to go. The new nuts look like some sort of soft material (bronze or something like that). Perhaps they are designed to deform a little when installing? Take a file to the edge of them to see how soft that material is. If it is soft, then there is very little chance of stripping the threads on the steering box.
Did you check the thread condition inside the steering box? Are they clear, or do they have some gunk from the old nuts still in them? Perhaps running a pick over the threads can remove anything that is left there and help new nuts to spin on better. Better yet, run a flat bottom tap into them to clean threads. Pack the slots in the tap with grease, so that the metal shavings would stay in the tap and not go into the innards of the steering box. You shouldn't have to do much effort on this, just hand tight in and out will do it.
When installing the nuts, don't over torque. When I have to torque the nut with the end wrench, I "calibrate" my hand by putting nut and bolt assembly into the vice, torquing it with the torque wrench to spec. Then I take an end wrench I intend to use and tighten the nut further until it overcomes previous torque setting. This gives me a feeling for how much force I can/should use on it when working on the actual part. Sometimes, it is like - two fingers on the end is just right, but pushing the wrench with three fingers is too much. You know - high end calibration...

 

Hunter.......

Thread dia: I am measuring the outside of the threads (ridges), and agree that the old one has rounded-down/mashed threads which make that dia. smaller.

Its hard to get my gauge down on the steering box holes, but when I did I got the following:
Small hole (high pressure line).........12.5mm
Large hole (return line).....................14.5mm

So, the new line dia for the High pressure line is 13.75 (ridges), and is going into the Small hole of 12.5mm......so, thats a difference of 1.25mm. So the depth of the threads should be at least 1.25mm in order for it to screw into the hole. Im not sure how deep those threads are, but the poor nut tries to screw into the hole, and gets super tight. Today I tried the other line, and it is also super tight......and as I slowly turn it clockwise while applying downward pressure, it starts to thread but then pops out. So, I think we have a problem with these two replacement lines with non-metric nuts on them.

I had forgotten about the Mitsubishi parts warehouse where I ordered another power steering line in the past.......I checked today, and they had the original OEM Mitsu. lines and I went ahead and ordered them.....paid twice as much, but it will be worth it if I don't cross-thread and screw up the steering box. So, Im gonna put this puppy on the backburner until the new lines come in. Then, I will do a thorough measurement and compare the Rock Auto lines with the Mitsu OEM lines, and post the results.

Good grief......this "simple" project really turned into a major effort. I probably just should have cut off the rotten bottoms of each line and slid a rubber hose & clamps on them as I originally had thought of doing.

Filing the threads......Good, so you give your "ok" on trying that. If the new OEM lines are identical to these gypsie lines, then I just might take a file to them to lessen the dia.......I dont want to be fighting with a wrench in that tight spot when trying to get these nuts into the steering box.

Steering Box thread condition......yep, they look fine......nice and shiny. I used a small thread sizing tool (like a small file, but with those 1.5 threads on one side) to skim around the inside of these holes, and they were in perfect condition.

Tap/die......I checked my kits, and did not have any that large. Will have to put that on my "want" list and pick up larger size sets.

Torquing the nuts......believe me, I will not be cranking down too hard on these nuts.....I would rather come back and tighten a bit more if it leaks instead of smashing that ORing to bits or cross-threading the threads. I agree with your "high end calibration".......one, two, or three fingers of torque........4 fingers and "pop goes the weasel". ha ha