Oil leak from union

Ok - so this a vehicle one - but car forums are full of experts on replacing lambda sensors and often a bit short on practical techniques.

There's a slow leak on the union that connects the oil feed line to the turbo on my diesel van (vw transporter).

I've tried cleaning and reseating the faces, I've tried using an oil seal gasket compound (I think it was Hylomar universal blue) - but I can't quite get that drip free seal.

Hot tips anyone?

Reply to
dom
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If this is a banjo union, then a pair of banjo union washers is what you need. These are steel washers with a thin rubber inner bit (around the inner circumference) that serves to seal the mating surfaces on banjo unions.

Reply to
Grunff

Sorry, no - like brake pipe unions - pipe with flared end and captive nut.

Reply to
dom

Replace the pipe... alos check for scores in the surfaces it seals to..

Reply to
The Natural Philosopher

A bit tighter perhaps. All I can think off is maybe a couple of turns of PTFE tape, but be sure that you arrange it in such a way as it doesn't 'fall' across the orifice.

Julian.

Reply to
Julian

Them's known as Dowty washers...

Julian.

Reply to
Julian

Thank you, I struggled to remember the name for a while then gave up :-)

Reply to
Grunff

================================== Undo the union nut completely and check that the pipe lines up centrally with the seating in the turbo. Make sure that the pipe is long enough to seat easily without being stretched. If possible slacken the turbo fixings and connect the pipe / union before re-tightening the turbo fixings.

Cic.

Reply to
Cicero

And I only know because someone reminded me about 5 years ago :-)

Julian.

Reply to
Julian

Might be worth trying a copper 'flare washer' which is a conical washer that goes between the sealing faces.

An AC parts supplier would have one or it may be possible to make one by annealing, cutting open and shaping a piece of 15mm or microbore tube.

Also try a little oil on the back of the flare to help the flare nut tighten up.

There is a small chance of a minute crack in the flared end so it would be worth taking a close look with a decent light.

cheers, Pete.

Reply to
Pete C

(around the

captive

Aneal the copper flare by heating to red and cooling, this will soften it as it will have work hardened over the years. The soft copper should snuggle up and make a tight joint, but if that fails cut a thin lead washer to sandwich between the flare and the fitting. (I've had all sorts of fun with 3/4" flare fittings on my 100kva induction furnace as they carry both the cooling water, and the drive current at several thousand amps and have used both techniques satisfactorily)

AWEM

Reply to
Andrew Mawson

A flare washer is inappropriate here.

Flare washers (sealing washers in general) work by being soft and getting squashed between two harder things. Works fine for a brass union into a brass fitting, but not so good against a soft copper pipe that's already a flare.

Reply to
Andy Dingley

I'm sure one /shouldn't/ be needed but the flare on the oil line may have got a little deformed or work hardened.

I expect the OP hasn't got a tool to redo the flare, even so the line may be too short, so a flare washer is cheaper and easier than a new line.

cheers, Pete.

Reply to
Pete C

By "inappropriate" I don't mean "un-needed", I mean "Won't fecking work"

Unless you seal the soft flare washer against something hard, it won't deform to make a good seal. An old copper pipe, even if work hardened, isn't a reliable sealing face.

Reply to
Andy Dingley

Gentlemen - before this gets heated - let me mention that it's a steel oil pipe.

Of course, this thread has just made me think about the implications of it being a steel pipe - like there was probably a sealing washer in there that I've lost.

Lost it several years ago in fact, when I had to do a head swap (an exhaust valve stem broke, struck a piston, ensuing carnage - all at

40mph tootling home from work, 2 weeks after buying the van, 85K, dealer maintained - these things happen. I thought it was a cambelt failure at that moment, but really was a spontaneous valve stem failure on an otherwise fine engine).

Of course all this happens 2 weeks before I go self-employed (hence buying a van), so I obtain a cheapy recon cylinder head, dremel the worst of the damage out of the piston crown - and regard the whole fix as a nasty bodge.

100K miles later, all is fine. It really has been a remarkably small leak considering I lost a seal.

Now I do apologise to all the posters here for running you round all 4 sides of a square - but if it's any consolation, it's done it's job and made me think it through.

I'm going down the vw dealers and getting them to look through all the nice parts diagrams...

Reply to
dom

Aha! If you can't get the washer separately it might be worth trying a little 'leak lock':

cheers, Pete.

Reply to
Pete C

I'm only aware of them as they're sometimes used for AC flare joints.

Also LPG fittings use soft copper olives on soft copper pipe.

As long as one or both sides deform to make the seal it should be fine.

cheers, Pete.

Reply to
Pete C

An olive isn't a washer. It has a sharp edge, so as to generate sufficient pressure to make a seal.

Reply to
Andy Dingley

Well, as you're an expert, how would you advise the OP fix their leaking flare joint?

cheers, Pete.

Reply to
Pete C

Remake the pipe. It's not hard, and then it's just done. Yes, I do keep the pieces on hand in the workshop to do this on demand, for the sizes of pipe (brakes and fuel) I'm likely to need to do it for. A good flare tool cost me twenty quid some many years ago and has repaid itself countless times.

At the side of the road, I'd use the Oyltite stick that lives in the toolbox for just such emergencies. It's bodging compound, not a gasket compound, and you apply it from outside the joint. Every home (full of oily engines and half-dead tractors) should have one.

Reply to
Andy Dingley

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