TheSamba.com :: View topic - oil lines leaking with aircraft fittings...how to prevent?

Wed Aug 29, 2012 12:32 pm

I've got a full flow remote filter system on my 71 Bay.
I've tried multiple types of hoses and hose clamps over the last 20+ years, but they all start to leak within weeks of fitting.
Right now I'm using aircraft style ends that aren't supposed to leak, but mine are after only a few thousand miles. Is there a trick to installing these?
Sealer used on threads? How tight should the compression fitting be on the hose?

Wed Aug 29, 2012 1:12 pm

- the angle of contact of the fittings varies with style and vendor - fittings must match!

- no sealer should be used or needed!

One solution which helps a lot is to use a pressure relief external filter pump cover (type 1, Gene Berg) which limits the maximum pump pressure by relieving pump output back to pump input. Thicker than a normal pump cover but does clear the moustashe bar. Stops filters from blowing up on cold mornings.

Wed Aug 29, 2012 2:35 pm

telford dorr wrote: - the angle of contact of the fittings varies with style and vendor - fittings must match!

- no sealer should be used or needed!

One solution which helps a lot is to use a pressure relief external filter pump cover (type 1, Gene Berg) which limits the maximum pump pressure by relieving pump output back to pump input. Thicker than a normal pump cover but does clear the moustashe bar. Stops filters from blowing up on cold mornings.

Thanks, I'm using the Gene Berg cover. All the red/blue -8AN fittings threaded in nicely. Not sure at this point where they are leaking, but it's getting worse. Need to clean them and see if I can track down the problem area. Using the blue oil hose.

Wed Aug 29, 2012 2:41 pm

Torque is extremely important on AN type fittings, too much is just as bad as too little. Follow the recommendations of the manufacturer to a "T". During assembly make sure the threads are spotless, even a speck of grime can lead to a leak under pressure. And as mentioned above stick to one manufacturer for each connection (male and female ends)

Wed Aug 29, 2012 4:25 pm

You have to determine where your leaks are. There are three possible locations and all are treated differently.
1. The hose to the the hose end.
2. The hose end to the adapter.
3. The adapter to the pump cover, filter, or the cooler.

For #1- Post a link or picture of the type of hose end you have. There are wads of different styles. To many styles to talk about the nitty gritty of each style. Aeromech with blue hose uses Push-Loc barbs that require no outer clamping. It takes a lot of force and a vice or the special tool to push the hose on the Push-Locs. They work great but I don't like them because they are not suitable for any road side repairs.
With my blue hose (or the lessor black hoses) I prefer just plain basic hose barbs and either 1 or else 2 common screw clamps close together. When using just the barbed fittings I don't like some of the newer brands since they only have 2 or 3 effective barbs which are also larger diameter. The older style have more effective barbs and it's easier to get the hose on with less stretching of the hose.
Then there is the type for looks only. It has a phony outer sleeve that just hides a normal hose clamp.
Then there is the industrial style commonly used on some hydraulic systems. It has the inner barb and also an outer sleeve that gets threaded down over the hose. Very critical to have the compatable hose and the exact hose OD with that style. You make those up on the bench.
Then the premade crimped hose assemblies. Most commonly the expensive S.S. outer sheathed/braided. They are very common on Dubs but I sure don't like them. Same rubber inner conductor as the cheap simple hoses. Same potential of failing. But they are so expensive people won't periodically replace them an consider them a lifetime hose. But with basic hoses it's best to replace them every once in a while.

For #2- The hose end and the adapter need to be compatable. Either 37-1/2 degree or 45 degree. SAE, JIC or AN. For the female swivel hose barb Parker's (-8/1/2" size only) has a double angle 37-1/2 and 45. Can't go wrong with that one. So make sure the angles are the same and when you snug it up to tighten it keep wiggle it to get the furthest in and best straight in seating.

For #3- Taper pipe thread on the adapter and either taper or straight female NPT on the item. NPT are not a sealing thread and need to be cranked tight along with using a sealant. On engines for some silly reason I havn't had good success with teflon tape. And likewise, Permatex Aviation 3H didn't hold up (It remains too fluid and soft). But for years have had totally wonderful results with Permatex 1A which is hardening.

No need for any leaks whatsoever :wink:

Wed Aug 29, 2012 8:06 pm

These are the fittings I used
http://www.ebay.com/itm/330378278496?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
Also used the corresponding male/male fittings http://www.ebay.com/itm/8-an-Male-Flare-To-3-8-NPT...35a4d98dff for the block and pump cover.
I think I did use the white Permatex thread sealer on those. I was pretty meticulous about putting them together first on the bench. I was hoping this was going to be the final solution to the leaks. I'll clean things up and report back when I can identify the leaking area.

Wed Aug 29, 2012 8:32 pm

It will be interesting to see where you find the actual leakage. I'm not familiar with the white Permatex. But if it's just teflon that might be the leak. The fittings look great but a statement about the hose end seemed confusing. "Works With All Braided Or Nylon Braided Line #8 Line". Hose O.D.'s vary all over the place. The blue hose we use is a pretty small O.D.

Wed Aug 29, 2012 9:24 pm

Desertbusman wrote: It will be interesting to see where you find the actual leakage. I'm not familiar with the white Permatex. But if it's just teflon that might be the leak. T

Could have been Loctite http://www.homelectrical.com/567-pst-thread-sealan...SE&kw={keyword}&gclid=CNjQlZDBjrICFWThQgodSVsApQ. Sold as thread sealer. Used it on the OP sender on my Vanagon with no issues. The hose is a tight fit. Took some doing to press the hose into the fittings before cinching them down. Perhaps the OD is too large and is causing the hose to distort. Brand is "Flex Lock".... made in USA. Which hose brand do you use?

Wed Aug 29, 2012 9:39 pm

Aeroquip. Seems like there is a Gates hose also that's the same. I don't remember what Aeromech uses.
Guess you still need to find out where it leaks. Nothing stands out as not being good.

Wed Aug 29, 2012 11:57 pm

Huh.
I had an oil cooler on my Bus engine and removed it, but used cheap premade hydraulic hoses from FleetFarm, right off the rack. They were quite affordable and had regular pipe threads which I sealed with some blue stuff I use on A/C fittings. Ran for several years with zero leaks. Took it off because I think an oil thermostat would be a good idea but I never re installed.
Zero leaks. Cheap lines.
Huh...... :-k
Well, good luck with those leaks.

Thu Aug 30, 2012 12:36 am

No tricks to installing these type fittings. Use them every day at work and have them on my oil cooler installion. No sealers or compounds. Clean threads. I prefer stainless tho, bullet proof and I get mine for free!

Thu Aug 30, 2012 1:41 am

Gary sent me a bunch of the copper compression collars that fit between the male ends off the pump (and back into the case) and the nuts for my AN8 fittings. Next oil change I do I will try them. That's the only place I've noticed any minute leaks. Ya know the kind you put in between anything like when you add a water filter in your home plumbing or like when you join pipes together. I used the white Permatex sealant for the remote oil filter housing fittings, no leaks there.

Thu Aug 30, 2012 7:20 am

Aeromech turned me on to the push-lok fittings with the blue hose and that setup has worked great. No leaking but as DB mentioned it's a bit of work to get the hose end fitting on. I've had no leaks and everything looks great.

Thu Aug 30, 2012 9:57 pm

srfndoc wrote: Aeromech turned me on to the push-lok fittings with the blue hose and that setup has worked great. No leaking but as DB mentioned it's a bit of work to get the hose end fitting on. I've had no leaks and everything looks great.

I too use Push-lok with good success. I tried Earls and had a hose blow.

Thu Aug 30, 2012 10:18 pm

Jody '71 wrote: Gary sent me a bunch of the copper compression collars that fit between the male ends off the pump (and back into the case) and the nuts for my AN8 fittings.

What's this copper compression collar you speak of?

Fri Aug 31, 2012 12:35 am

Its just a round washer with a 37 degree angle to fit between the mating surfaces of the -AN fittings. Since its copper, it will compress and sill between the harder surfaces. I've used them for 3000 psi testing and above. Can't remember what there called. Got some in my tool box, I could go look. Boyd-shims or somthing like that. I have one whole drawer in my toolbox at work deicated to -AN fittings of all sizes and shapes. Alot of good laughs around here when techs use the wrong hardware and things go boom.

Fri Aug 31, 2012 9:46 am

Thanks Jim,

But what the hey. AN fittings have been around since the second world war. On millions of aircraft, vehicles, ships, industrial equipment, and everywhere else for over half a century. Neil Armstrong would have flown them to the moon and back.
I worked in the fluid power industry and with Gates, Parker Hannifon, Weatherhead, Aeroquip and other brand fittings and hoses. AN, MS, JIC, SAE. The fittings worked as is. And I even have some 30 degree pipe swivels on my bug.
But this thing about conical copper sealing washers is a whole new thing. Really curious, do you have a brand or part number?

Fri Aug 31, 2012 10:34 pm

OK, after cleaning things up, it's definitely leaking from the spot where the hose presses into the collar on the AN fitting. For some reason it is leaking at both connection to the remote filter, but not at the block end. All the threaded connections are solid and free of leaks. Probably a hose OD issue. The hose was a very tight fit into the collars. Hard to believe they could leak, but maybe they developed creases on the inside when I tightened them down. They are just about as tight as they will go. I'll try and cut an inch off the end of each hose and refit them with a little less tightening. If that doesn't work, I'll have to try a different brand of hose.

Sat Sep 01, 2012 1:14 am

SECO 7C4 (these are for -4) SECO SEALS,INC 714-546-3478 Yea, ya don't need em. I use these -AN fittings over and over again testing these aircraft parts and never no problems. Wrong hose on that fitting that did't loc. They have to mate. The crib here makes our hoses (custom) fit. It's one big hardward supermarket and aircraft quality.

Sat Sep 01, 2012 7:35 am

DBM, see if you can contact Gary, and ask him about what he sent me.