Schaublin 135 oil line connections won't seal

In the course of my getting this machine up and running I had to remove the haudraulic oil tank, pump and associated lines. This seems like no problem as they are attached with very normal looking banjo fittings with copper washers. The issue is now I can't get the damn thing to seal. I think it is the line with the aluminum spacer shown in the attached photo but I am really stumped. I replace the washers ever time they are tightened, have cleaned and de-burred the mating surfaces and tried various levels of torque (does anyone have an actual spec for these?) I have tried it with washers on either side of the spacer and without, made a new spacer etc. but I keep ending up with a puddle of fluid around these connections and on the floor of the machine ever time I run it for even a few minutes. It isn't a small leak and makes a huge mess.

Ideas?

I am about to wash everything down with solvent and resemble all the lines with RTV If i had any hair left I would be pulling it out.

Hi Whidbey,

maybe you have more luck to seal the joints by using bonded seals or so called Usit rings. they come in a lot of different sizes. a benefit is that these rings are reusable.

BR,
Bertus

Thanks maybe I will see if I can find some of those. Seems like it shouldn't be nesecary but I need to try something new. Having them be reusable would be a good thing.

Luke

You probably already checked, but are you sure non of the bolts are bottoming out so there is only low compression of the seals?

Never used it with banjo fittings but maybe something like hydraulic seal from loctite could help, applied very thin to the mating surfaces.

I'd be inclined to try annealed copper washers to act as gaskets.

Yep all the ones i have used and seen are fitted with copper washers.

They must be annealed, i.e. heated to a reasonable temp then dropped into water.

They should take up any errors especially if someone has overtightened it in the past and distorted the housing a little. really should have no problems with them.

Try new washers and anneal them if they are not soft.They do work harden.....

The washers I purchased and am using say they are annealed but I suppose I can anneal them again and see if that helps anything. It is simple enough to try. It seems like there must be a burr or scratch I am missing somewhere

Luke

I thought I had figured it out, but unfortunately that is not the case. I removed the offending tube and checked the mating surfaces in detail. While they are smooth they were not flat in the area were the washers sit, which was somewhat depressed if that makes sense. I carefully filed and then sanded the surfaces flat and square, reassembled with yet more washers and proceeded to end up with oil all over the place again. I think actually the top connection is improved but the bottom is not.

I am talking to a local supplier about bonded seals but still really don't understand why this is so messed up. I think it is the aluminum spacer that is the main problem now, I have tried it with and without copper washers and it seems to leak more without the washers which makes sense although the aluminum is so soft I thought it would not matter.

L

What pressure is this running at?

Ever seen a Lock-O-Seal? It's a O-ring, bonded to the inside of a washer. You could make up your own, un-bonded version pretty quick with a bit of lathe work. A rubber O-ring fatter than the thickness of the washer, and another washer as back-up on the outside.

I used to work on a Jet Trainer that had a PILE of banjo fittings, all aluminum banjos, steel nuts, and copper washers. Winter weather was a sonuvabitch as the different contraction rates would cause hydraulic leaks at more or less random, once the jets were hauled out into the winter sunshine at 30 below C.

How hard you torquing down on the crush washers? In my experience, it still takes a pretty good pull on the wrench to get anything less than a absolutely perfect set of surfaces to seal on a clean, dead soft copper washer.

Cheers
Trev

Thanks Trev, good point about making up a couple seals with o-rings. That would be easy enough to try.

I sealed what I think is the offending joint with blue rtv yesterday, not an ideal solution but now I can be fairly sure it isn't leaking and can look for other sources if there is still a problem.

As for torque they are good and tight but nothing crazy.

Someday I won't have an oily floor

Luke