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My brake line elbows are leaking on my Grove aluminum gear legs - Options?

moespeeds

Well Known Member
Friend
The AN4/1/4 NPT elbows that screw into the top of my aluminum gun drilled gear legs are leaking. Looks like they were both installed dry, so I've got to get them out to put PTFE on them.

I tried cutting a bit for clearance as you can see in the photo, but there isn't enough room to unscrew that fitting without it hitting the bottom skin. So basically it won't rotate a full 360.

If there was a such thing as an elbow with a short end on the AN side, I could cut these off and screw that in, as I only need about 3/32" more for clearance, but a google search was fruitless.

Any other options here besides pulling the gear legs?
 

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Moe there isnt. And not enough room to rotate the fitting out, reseal it and reinstall. Without cutting a big hole in the floor of the gear tower, the only option I know of is to pull the gear leg.

Tom
 
What Tom said.
Unknowingly, I originally installed those fittings dry.
After putting the hydraulic oil in, yep, they leaked.
Removed the legs, sealed the fittings reinstalled the legs and no more leaks.
Lesson learned...
It is true that the fittings could maybe be elsewhere to permit maintenance without having to remove the legs...
 
There is one possibility that I came up with in the shower this morning.

In the race cars we use an Aramid PTFE brake hose that's ultra flexible. I'm wondering if I could cut out that elbow fitting, put in a straight fitting, then replace the hard line with an Aramid hose with a 90* fitting on the end...

I'll order a -4 straight and the 90* fitting so I can assemble on the bench and test the clearance.
 

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While you're at it, take the time to put some kind of wear protection between that (aluminum?) line and the very tight hole that it runs through. A leaking fitting might just weep, but when the skin saws through that line over time it'll leak a lot faster.
 
The builder has tubing in there, it's just slid up and out of the way in that photo. If I go the flex line route I'll have to drill the hole bigger anyway so I'll put snap bushings in there.

Why does Vans use these giant -4 fittings for brakes on these tiny little calipers? We use -3 lines to stop 3,000 lb cars.
 
There is one possibility that I came up with in the shower this morning.

In the race cars we use an Aramid PTFE brake hose that's ultra flexible. I'm wondering if I could cut out that elbow fitting, put in a straight fitting, then replace the hard line with an Aramid hose with a 90* fitting on the end...

I'll order a -4 straight and the 90* fitting so I can assemble on the bench and test the clearance.


Ah...the Shower Solution! That's the best problem solver there is, nice job thinking outside the box.;)
 
probably not enough room to get a straight nipple AND a 90* hose end in there, whether a block style fitting or not.

The shower was the problem---you have to wake up from a dead sleep!:eek:

Tom
 
Why not just run hard lines down the legs like the plans call for?
Would way be easier than pulling the gear.
 
Why not just run hard lines down the legs like the plans call for?
Would way be easier than pulling the gear.

These are the Grove airfoiled gear, so there is no fairing to cover the external brake line.
 
Why not just run hard lines down the legs like the plans call for?
Would way be easier than pulling the gear.
It looks like he has the airfoil shaped gear legs so he probably isn't using gear leg fairings, so there wouldn't be anyway to cover the lines.
 
It looks like he has the airfoil shaped gear legs so he probably isn't using gear leg fairings, so there wouldn't be anyway to cover the lines.
Confirmed
The Airfoiled Gear has an internal oil line in the leg.
And no fairings needed.
 
fitting

Look for a 90 degree street elbow. NAPA has them as well as MSC Hard to tell from the photo but I think they would work. if the first one you find doesn't work look for a different manufacturer. They vary considerably. You may need to customize a wrench to fit. Then a straight AN fitting or a special hose with a male pile thread on the hose end. I personally don't like the nylo flow tubing but that would also work.
 
fitting

search JEGS 63082 for a picture of the type fitting I mentioned. Don't worry about the brass or the non AN fitting, they were used for the oil pressure line on some certified Pitts aircraft.
 
There is one possibility that I came up with in the shower this morning.

In the race cars we use an Aramid PTFE brake hose that's ultra flexible. I'm wondering if I could cut out that elbow fitting, put in a straight fitting, then replace the hard line with an Aramid hose with a 90* fitting on the end...

I'll order a -4 straight and the 90* fitting so I can assemble on the bench and test the clearance.

My recommendation - get a buddy to help you get the aircraft securely up off the wheels and pull the gear leg. It will take two people about a day to do it. You will spend a lot of effort to find out what Tom said - there ain't enough room in there to do it another way, unfortunately, and if you mess it up, you'll have to pull the gear leg anyway. Also, if you don't have the "good" nuts on those gear bolts, it would be a good time to install them.
 
fitting

I didn't mention the obvious, that the 90 degree fitting needs to be cut off as far away from the gear as possible. Die grinder with thin disc or cutoff blade. Then some vice grips to remove the remainder. The street elbow with AN 616 straight fitting will only require a small change in the tube length. or can the hole that the tube goes thru be elongated and the tube be moved slightly?
The nylo flow with brass fittings may be the best option. My main objection to the nylo flow is the heat from the brakes which will not be an issue here.
 
Well, there "is" an alternative, that hasnt been tested, nor engineered for that matter. Now I'm not saying do this, "but" on the inside of the gear tower, mark an area (if you can get to it through the lightening holes) and open up an elongated hole somewhat where the fitting would be. Purpose is so the fitting could be turned out and in without hitting the floor.

I would think---me thinking out loud which is a BAD thing (right Ken?), there is enough substantial tower structure in the area that opening an elongated hole 1x1.5 inches would solve the issue. Getting access to do this, well thats another story.
Just saying. Alternative to pulling the gear legs.

Oh and response to Jim's statement about variances in fittings, yes in industrial to a point, NO to actual Mil-Spec AN/MS/NAS fittings. Industrial generally meets a SAE spec, although alot of industrial manufacturers have there own versions that resemble a standard fitting. Real AN/MS/NAS fittings all match the same drawings, thats why they are interchangeable, and are include in FAA, Standard Part. "Some" of the old Eaton Weatherhead fittings that NAPA used to sell (I think they have mostly gone to Gates now) did interwith change a MS number, as shown in their catalogs. Check that now, or just use a real Mil Spec fitting, OR one that meets the drawings for dimensions. Careful----some look a like fittings are not the approved material!.

Tom
 
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fitting

The reason I mentioned the brass automotive fitting is that it requires less clearance than the AN equivalent. If you find the right automotive or industrial fitting the clearance requirement is almost the same as a straight AN fitting. The only issue with the automotive street elbow is that you will probably need one or more modified wrenches. A offset open end wrench, with different angles on each end, might also work.
The parts would be:
90 degree street elbow
AN914-1D if you keep the aluminum tubing
For Nylaflow tubing:
Aircraft Spruce part number 05-04349( this is heavy wall tubing rated at 2500 psi. Used for decades on EAB for brake lines)
Fitting is 268P
This would be so much easier than removing the gear.
 
Brian, NPT banjos are tough to come by, but a great idea. The tapered port in the gear leg is the issue. You'd need a custom NPT stem with a hex to secure it in the gear leg---installed height may be a factor--, then a straight stem for the banjo. A NPT male to ORB Female bushing could work, but again the clearance may not allow all of that to get in the confined space.

Even a NPS (NPT swivel) fitting probably wouldnt clear, AND with only an internal O'Ring to seal the stem, from experience the can leak at low pressures.
A NPT Male to Straight thread (7/16-20) insert might work, but you'd have to pull the gear to install it anyway.

The Banjo is a good idea though---if during the manufacture of the gear leg, the port were a straight thread instead of an NPT tapered one.

Tom
 
Try this

Hey Moe,
I don't think you need to remove the gear legs. If all you need is an additional 3/32 inch of clearance I think you can remove the inner three bolts that secure the end of the gear leg and this should allow the leg to pivot slightly to give you room to extract the fittings. The large outer block is designed with a slight radius in it to allow the gear leg to flex around the radius rather than a square corner. There just might be enough play to rotate the gear leg enough to give you that 3/32 inch. Those three bolts are a lot easier to pull than the two that are buried the gear tower.
 
I'd bite the bullet and remove it for what it's worth..
An engine crane and sling around the engine mount and away
you go.
 
Im using 1/8 OD (yes, same as fuel injector lines) for brakes on the Rocket. This uses the cone compression fittings to seal and so far has been flawless. Ill bet a 90 degree compression fitting will thread into that leg once the much longer AN fitting is removed. You would have to run new hardline up to the flex hose above the rudder pedals, but the 1/8 hardline is a breeze to work with.
 
I think that'd be really useful.

I ended up cutting out the old fittings, and replacing them with 1200 PSI brass street elbows and AN4 straights. I also ditched the aluminum hard line for super flexible aramid PTFE.

Saved me from pulling the gear legs, and now it's actually serviceable. I have new bolts and the heavy duty nuts on order, and I got a set of the bolt locks so I don't have to torque in the gear tower.

Thanks guys.

Tom, you're an expert on this stuff. Have you ever seen or used anything like this?

View attachment 15239

https://www.ebay.co.uk/itm/171414187984?hash=item27e914efd0:g:cqYAAOSwDk5T428f

Would it be useful here?
 
Brake Line

Moe-
Nice to see my idea worked after 12 days of "gotta remove the gear." For the "next guy" the 90 degree fittings are also available in AN but I believe they require just slightly more clearance than the automotive/industrial.
 
Leaking Elbow

I’ve be involved with plumbing for my entire life . Pipe dope works almost all the time ………. Recently we had some gas and water fittings that leaked no matter how tight we made them up with pipe dope . We now put them together with West Epoxy instead of pipe dope . Works perfectly.
 
I'll add this---
I didnt see this as a -4 with either 1/8 or 1/4 NPT. The bolt has a female Torx hex head, and you'd need a really short Torx bit with a wrench in the space allowed. Would be better if there was a hex on the stud under the banjo. The other thing is the brakes are under alot higher pressure that your fuel system, and with that, any movement in the banjo 'may' allow some small volume of air to migrate into the system. The more air in the system, the softer the pedal.

Still easier to just reseal the AN fitting and go fly.

Tom
 
Moe-
Nice to see my idea worked after 12 days of "gotta remove the gear." For the "next guy" the 90 degree fittings are also available in AN but I believe they require just slightly more clearance than the automotive/industrial.

Turns out I'm the next guy. Any and all details you or Moe can give me would be extremely helpful. There's no way I'm pulling a gear leg at this late stage. Something else occurs to me: I wouldn't connect any aluminum to a brass fitting because of galvanic corrosion. Your thoughts?
:mad::mad::mad:
 
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Brass fitting

To elaborate on what I previously posted, at least some certified factory Pitts aircraft use the brass automotive "street elbow" on the oil pressure port on the aluminum accessory case. Never heard of a problem with one. They were using those fittings in early to mid 1970's.
 
Perhaps we can help!

---- I have the fittings you requested in stock. We made these to solve a problem
on another project, but it appears they are exactly what you may be looking for,
as they are 1/4" shorter on the AN side. Just let me know if you would like a
couple of them. Regards all, Allan-:D
.
 
Success... and Failure...

The good news: after borrowing angle wrenches from Dave Pohl, relieving material from the opening edge and stretching the floor sheet metal a bit, I gained enough swinging room to remove the fitting. The threads in the leg looked ok, if not a bit gummy.
AM-JKLUl1cvNIwyf_rshr0VKfSOvkMRxoD_usjo0_MrnrV2cFiQK7XVw_mOhjsFs27BJOLu4O1ekOP2Ies4AdyAj6IdsL00Fftsfy3lHRO4LEgqd9Dps_sh1Mtzj3QzdELMKB09ZgEZeoBAQTZXn8UsZVW9S=w900-h600

I tried my best to clean off the fitting (again, a bit gummy), added fresh Permatex #2 to the threads and managed to get it back in. I carefully clocked it an additional turn (it felt TIGHT) and cleaned the area a bit. Also checked the left side, which looks pristine.
AM-JKLV1MgbSp2JhfFKn4IJe7UXlnxIAg6JUK9W_OVbwdSEfk4-lbPDWXl7ZFEZ_ftAUCCwtE5Tq6EdSCE6Si3nmzYYjf3Wy5XO_CAak9JsNqjR9TN5o-zpHzZ1gU6Amjj8z0JSIaqxBm_T-BknTvHp3mT_X=w900-h600

I refilled and bled both brake lines, and after waiting about an hour I checked the right fitting. Looked like it might be oozing; climbed in and checked the brakes. Left: perfect. Right... gradually dropping. The leak wasn't as bad as the original, but it's still unserviceable.
AM-JKLWox391ssNFUa1y34TEkl9FNaV6LZ-RunYQOpXN0ovrxfbPYfu4FJiJ4x7_EaOnIMztyYL1CpyPUj24OeZ6M99hw5cRAnep7YMnStuqd6hUpCdIve51JU-E0c80Fv_5rftLh6t0-0NPVENJVxm4PxA8=w900-h600

I can't help wondering if the Permatex is incompatible with the Aeroshell Fluid 31 Hydraulic Fluid I'm using; it almost seems to dilute it... but that shouldn't be the case; all other fittings are sealing fine. The next step: remove the old fitting, clean the leg threads as well as possible and try again with a new fitting. Pondering using pipe dope but don't know their compatibility with the fluid. The West Epoxy is tempting... but if it doesn't work it will probably create a new set of problems. Why is the left leg fine and the right leg a nightmare?! Moot point, Marty... just work the problem. As always, suggestions are welcome.
BTW: Duly noted, Allan... I just ordered the Ultimate Gust Lock from you guys so I may be in touch for one of those fittings.
 
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Sorry to hear that Martin, FWIW, I have the Grove Airfoiled also, and once did remove and re-install the gears because I had not sealed the fittings originally.
I then used Permatex #2, on the gears and brake calipers.
At one point, hydraulic oil (I use Royco 782) was found seeping from one of the caliper's upper fitting...
So I removed both fittings, cleaned the threads and the calipers and used Permatex 567 instead.
No leaks since.
I just hope that the upper gear fittings with the #2 sealant will hold.
As with you, it seems that the #2 sealant does its job in some cases but not in all cases... Maybe cleanliness on instalation???
I can't say...
 
The permatex I have sitting here on the bench says “adjustments can be made up to 24h after application”, leading me to believe there is some curing process; would giving the sealant time to set make any difference?

I’m watching this thread, as I have Grove gear for my -8 project.
 
The permatex I have sitting here on the bench says “adjustments can be made up to 24h after application”, leading me to believe there is some curing process; would giving the sealant time to set make any difference?

I’m watching this thread, as I have Grove gear for my -8 project.

Is permatex designed to be a thread sealant? Why are people reluctant to use a product that’s designed to be a thread sealant, like locktite 565 or the higher temp rated 567? This whole thing started because the OP bought a plane where the builder used ez turn fuel lube….
 
Correction

I have to correct my previous post where I stated using Permatex #2.
I used in fact Permatex Hydraulic Sealant #54550
Still, that sealant failed in 1 of 8 location, (Master cylinders, Calipers, Gear legs)

I now use Loctite #567
 

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I ended up cutting out the AN4 elbow, and replacing it with a 90* brass street elbow and an AN4 straight. I got rid of the hard line and ran AN4 stainless braided, straight on the M/C side, and 90* elbow on the gear fitting side. This did require some cutting of the gear leg floor to "move" the existing holes to allow the elbows on the braided line to mate up. Sealed the NPT threads with Loctite 567.

If galvanic corrosion between the brass and the aluminum is an issue, I'll check it at every annual. It's now a 5 min job to swap out that street elbow. We use them all the time in the road race cars I've been building and maintaining for over 10 years now, under far harsher conditions than the average RV sees, and have never had a problem.

I'll post pictures of the install later tonight. If anyone has grove gear, I'd highly recommend doing something to make that fitting serviceable.
 
---- I have the fittings you requested in stock. We made these to solve a problem
on another project, but it appears they are exactly what you may be looking for,
as they are 1/4" shorter on the AN side. Just let me know if you would like a
couple of them. Regards all, Allan-:D
.

Alan, are those 37-degree flares? In the photo they look kind of like 45-degree flares as would be found on automotive brake systems.
 
As always, suggestions are welcome.

Quit making yourself crazy. There are only three or four threads engaged. Drop the gear leg, run a good tap in the hole. Tap about 2 threads deeper. Plug the axle end. Screw in the AN elbow. Plumb an air line to it and bubble check. Reassemble. Done.

Practically any thread sealant will be fine if the threads are good.
 
Follow Up: more bad news

At the hangar with a new fitting; before draining the system, inspected; the right side didn't leak much overnight. Tested the brakes, both soggy (not a good sign). Removed the right fitting again, cleaned the threads thoroughly... then noticed a fresh drip from the left side. Apparently it did not stand up to pressure after the sealant had been exposed to the fluid and pressure multiple times. Contacted Aeroshell to see if they have recommendations on sealant. I won't try #2 again. I bailed for today to allow the discouragement to pass. We'll see what tomorrow brings.
Quit making yourself crazy. There are only three or four threads engaged. Drop the gear leg, run a good tap in the hole. Tap about 2 threads deeper. Plug the axle end. Screw in the AN elbow. Plumb an air line to it and bubble check. Reassemble. Done.
Practically any thread sealant will be fine if the threads are good.
Good points, Dan, as always... but I will say there were more threads than that engaged. As to your last point, probably true... but I should have enough thread engagement for the sealant to work. Maybe it does come down to the Grove threads, but I will experiment with other sealants before removing both landing gear. Installing those stinking gear legs was the hardest thing I've ever done on that aircraft, and the job will be worse now with more wiring and plumbing routed, not to mention realignment. I will do everything in my power to avoid that. Yes; a wise builder might have tested the legs before installing them. I'm not a wise builder; I'm a novice builder in the process of obtaining wisdom the hard way. Which brings me back to your first point... it's kinda too late for that. ;)
 
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Is permatex designed to be a thread sealant? Why are people reluctant to use a product that’s designed to be a thread sealant, like locktite 565 or the higher temp rated 567? This whole thing started because the OP bought a plane where the builder used ez turn fuel lube….

A very good question. I started using Permatex #2 because that's what Van's recommended to me. It's worked well everywhere else... just not here.
 
I just got done with a similar fitting issue on my RV-12iS. I wish I could say this one thing fixed it. The changes I made after a lot of research and talking to Vans.

- Clean all the threads carefully with acetone or alchol
- Hand tighten the AN fitting and then 1.5 to 2 turns with a wrench
- Don't turn the fitting back to clock it this will disrupt the sealant
- Leave it >24 hours before adding fluid


From the Permatex datasheet

Assembly is operational after 4 hours, full cure is affected after 24 hours.
 
.. but I will say there were more threads than that engaged.

Either 8 or 9 on a fitting, depending on where you count. I count five showing, see below. Not saying it can't seal with three or four engaged. I'm saying there is plenty of material to cut a better female thread.

Maybe it does come down to the Grove threads...

Two careful rounds with a sharp tap can do wonders.

I started using Permatex #2 because that's what Van's recommended to me. It's worked well everywhere else... just not here.

Kinda makes a fella think about what might be different here, given one component of the interference fit was manufactured to a standard.
 

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Photos of how I did it.
 

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Either 8 or 9 on a fitting, depending on where you count. I count five showing, see below. Not saying it can't seal with three or four engaged. I'm saying there is plenty of material to cut a better female thread.



Two careful rounds with a sharp tap can do wonders.



Kinda makes a fella think about what might be different here, given one component of the interference fit was manufactured to a standard.

Dan is right.. I’ve had threads in aluminum intake manifolds (car stuff) that wouldn’t seal no matter how much goop, or tightening. A turn or so with a quality pipe tap and they seal wonderfully with regular methods. I think when a manufacturers tap gets worn, it could effect sealing.
 
"See below"

I read all of the posts with the seriousness of fittings in , fittings out, this sealant on, this leak here, and read and read to get to the solution. Then Dan H commented with removal and tapping the threads. More entries and then the thread engagement count started. Directed to "see below" I studied the photo and immediately started laughing as the fitting had been turned into a porcupine. So funny.
Great visual Dan.
 
Dan, when wrote that, I just knew you would examine my own photo, count the threads and dispute my claim. I would have done the same thing. I could have sworn I got five complete turns minimum on that fitting (it started with four)... but you're right; it just shouldn't be that tight that quickly. Right now, after doing my own thread sealant research to confirm what was advised here, I think I'll go with Locktite 567. And I definitely want to figure out a way to chase the threads but I want to think of a safe way I can do it in situ. A standard tap won't fit; maybe I can have one modified to work in the confined space. I will do anything to avoid pulling the gear... but you knew that. I just can't bear to go through all that again until all other possibilities are exhausted.
Thank you all for your patience with me in this matter.
 
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Particular Tap ?

So, to tap a NPT thread, would that require a particular tap or a standard one is good to go ??
 
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