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leaky petrol pipes

As you've probably gathered I'm getting the austin ready for an Mot, having now sorted the engine and got it running I have encountered a problem that I had forgotten about. A leaky fuel line.

My 7 is a 1930 RL saloon (built in 1997 - 2002!), so a scuttle mounted tank, but I have a later side draught zenith and manifold. The plumbing utilised the original fuel tap with a reserve, below this I fitted an in line lawnmower style (but new) brass valve.

Having had a super leak, and the MOT man turning his nose at it I did away with the original tap, made a flange, pipe to the 'new' tap, etc. However I always had a slight leak from the connection below the new tap, basically the connection you allways break to remove the fuel pipe leaks. It is the old style socket type

I've tried the connection dry (leaks), PTFE tape (leaks less), hylomar (as ptfe tape), ptfe tape and hylomar (leaks after 2 days), silicone (messy and useless). I have examined the parts till blue in the face and there is nothing wrong with it.

When the tap is off you get no leaks, and when running the fuel that has leaked evaporates, however when I or the MOT man leaves it standing at the test station, you get a very slow drip onto the exhaust. The MOT man smells petrol and I get a flea in my ear about fires and all that rubbish

Are there any sealants that will sort this, or shall I resort to soldering the bugger up?

Out of interest, best insurance quote so far is £75, nearly as cheap as joining the PWA7C and using the recommended club insurance, however I see an electronic membership of the scottish club is £5........

Re: leaky petrol pipes

My good friend Steve Jones would probably recommend Golden Hermetite in the joint. I would agree, having tried it on his advice and it works! I might add that, in theory, a shellac based sealant would not dissolve in petrol (though it will in meths) eg Rustin's knotting. Haven't tried this, though.

Regards, Stuart

Re: leaky petrol pipes

I'm not sure if the joints you have can accomodate a washer but I use "Doughty" washers on my petrol tap conections and this seems to seal them.

The taps have become very stiff over the years, I am presuming because of the lack of lead to lubricate them. I take mine to bits each year and give the taper a good covering of copperslip or the like, seems to keep them free and stop them weeping.

Good luck...

Ruairidh

Re: Re: leaky petrol pipes

Stuart's good friend Steve Jones does recommend Golden Hermatite in the joint. Works on leaky radiator taps too. I normally find I have to re-apply after about two years. Silcone will not work at all as it is dissolved by petrol. One of the 'properties' of modern petrol is its ability to leak in situations where traditional petrol wouldn't - as well as bu**ering up Oxygen Sensors if you live in the South East

STEVE

Re: Re: Re: leaky petrol pipes

Steve

Not sure if you have a fuel pump or not?
My pump (standard Ruby mechanical) leaked around the pressed steel cover which is held on by one bolt on top. The rubber gasket didnt seem to seal well. I eventually got it to seal, but I presume Golden Hermetite would have worked here as well? Is it specified as resistant to petrol?

Steve.

Re: Re: Re: Re: leaky petrol pipes

Golden Hermatite has worked very well on the tap on my petrol tank pressurised to 1 psi.

Re: Re: Re: Re: Re: leaky petrol pipes

Whether Golden Hermatite is specified as resistant to petrol I do not know but the experience of many who have tried it suggest that it is.

I was always of the view that it was a similar material to Blue Hylomar. Recently however, a friend has tried to seal the petrol tap on his 14/40 Vauxhall with Hylomar and it didn't work at all so, perhaps, there is a difference.

As to whether it would work on the fuel pump problem, perhaps, but these should not leak at the cover joint in any event so it might be best to find the cause rather than treat the symptom.

STEVE

Re: Re: Re: Re: Re: Re: leaky petrol pipes

Many thanks for the replies,

No chance of fitting a washer as the fitting is a conical socket, nor have I a pump. Sounds like Golden Hermatite is the way to go. A piece of PTFE tape partially blocked my pipe last night, ended up stinking of petrol all night!

However I've never heard of the stuff, and dont recall ever seeing any at the motor factors, where can I get it from?

Hedd

Re: leaky petrol pipes

Hello Hedd,

Why not think about making a permanet repair?

Petrol dripping onto a hot exhaust can result in a fire and when you have a fuel tank perched just above you knees it would seem to me to be even more desirable to eliminate any chance of an enforced performance of fire drill.

Now I am not really certain what you mean when you say that the faultly "joint" is "an old style socket type." I would guess that you have a solder on nipple type but, no matter, it is obviously leaking.

I would detach the said leaking joint, cut off what I presume is a soldered on nipple, and obtain a brass fitting which would convert the output of your tap (I suppose 1/4" BSP but you would need to check, it is just after 1am here and I am not thinking too straight)to a 1/4" pipe fitting (or whatever OD pipe you have going to the carburetter) of the type which uses a copper olive to provide a seal. (I am assuming you have a solid copper pipe fitting going there)

If you use a piece of rubber type petrol hose to feed the carby, then a fitting with a "barb" would be the answer.

I have no doubt that you will achieve a seal with the Hermatite or whatever, but there must be something wrong with the connection if it leaks and I would not want to take any chances.

The brass petrol fittings are not expensive, and the only difficulty which you would have to overcome is getting the right sizes, but a clever devil like yourself would be able to sort that out.

I actually have an SU on my Chummy and that is fed via a braided petrol hose which screws directly onto the tap on the tank.My only concern,and I think you will be in the same boat, is that there is only just enough "head" on this set up as the inlet on the carby and the output from the tank seem to be nearly the same height, but I have not had any fuel flow problems.

Best regards

Barry R.

Re: leaky petrol pipes

I would agree with Barry about effecting a repair. Often the cone shaped nipple on the end of the pipe has been lapped into the tap to ensure it has a good seating. As it is a tapper for every little you take off of the surface it goes deeper into it's mating assembly ( the tap ). When you then screw down the locking collar to tighten the joint the collar binds on the mating assembly before full bearing down on the tapered nipple. To carry out a tempoary repair gentle take a file across the open end of the threaded collar to reduce it's height and to allow it to force the nipple into the assembly.

You often find the oil gauge pipe union weeping for the same reason.

I hope I haven't cause offence with all this talk of 'nipples'

Re: Re: leaky petrol pipes

Hello Hedd,

Now that I am awake I have just had a further thought about your "seepage" problem.

You mentioned earlier about "flanging" a connection so I wonder just what sort of ends are on this petrol tap of yours.

I trust that your new "lawnmower" petrol tap is made with ends to suit the sort of connection you are using.

This can all be a tricky business.

If you have a tap which on the end you are trying to connect with is simply threaded 1/4" BSP (or possibly more correctly BSPT) with a plain bore that would be perfect for a suitably arranged BSP connector,(like say, a barbed adaptor) as the sealing would all be done in the threads. If you are trying to mate up a nipple type connector directly with this though, and the tap is not suitably arranged to accept such a connector then you will find it virtually impossible to get a proper seal.

I am also visualising the tap as having a male 1/8" BSP thread on the tank end and I suppose a male 1/4" BSP (perhaps BSPT) thread on the "connector" end.

I wish my scanner was working, but it isn't, because this is a situation where description is difficult but a picture would show all!

In essence though, you may just need a 1/4" BSP fitting to 1/4" pipe nipple type adapter and the original nipple and nut may be perfectly OK (although bear in mind Malcolm's wise words)

Why not take the petrol pipe and the tap down to your local purveyor of brass fittings and get their advice.

Just a word of warning though, the thread on the carby body is (or should be unless it has been mucked about with) a metric type so the fittings there are "precious"

I also think that the correct name for the adpator I was talking about in by wee small hours message to you previously would be "1/4" BSP to 1/4" pipe with olive" connector but make sure that you establish what your pipe size and threads actually are.

Am I right in remembering the thread on the fuel tank being 1/8" BSP, or is that just further evidence of the decayed state of my mind?

Regards

Barry R.

Re: leaky petrol pipes

Barry's advice to effect a proper repair obviously the most desireable course, but in answer to your question as to stockists of the golden goo, my local motor factors (Allwoods) turned out to be stockists and I'd never noticed it before! I don't think it's terribly arcane. A phone call or two should sort it if you're so inclined.
Allwoods, bless them, are OK. Every now and then they ask me "What's it for?" and just sometimes I crack and say "1930 supercharged Austin 7" and the response has always been, "You'd better have some discount, then!". I think unspoken is "You poor bu**er!"
Not guaranteed to work with all motor factors...


Regards, Stuart

Re: Re: Re: leaky petrol pipes

The tap is a new job (well nealy five years old now!) and is ex Complete Automobilist with the pukka nipples, pipes etc. I think I will drain the tank and have a harder look at the nipple, valve and nut, perhaps as Malcom suggests it has bottomed out. If not I will try some of the magic goo before soldering the sod up, that will fix it.

Re: leaky petrol pipes

I have known the solder to crack on nipples of this sort leading to a slight leakage as described. Certainly resoldering cured my problem.

Another thought, if you are using solid copper pipe, unless the pipe is bent to a precise fit, the taper of the nipple will hit the tap at a slight angle and the union nut will not exert enough pressure to pull things up square. Try tightening the pipe union to the tap first, then see if the carb end of the pipe aligns correctly with the carb fitting. Bend the pipe until it does. Repeat, fitting the carb end first and checking for alignment at the tap end. Keep checking one end and then the other until everything fits.

Well it worked for me anyway!

Martin

Re: Re: leaky petrol pipes

Hello again Hedd,

Have just had a look on Complete Automobiliste's site and reckon that you must have either their P/N 342 or 343. Both are top quality taps and should seal perfectly with soldered nipples.

I would definitely give Martin's advice a try as the tap should seal perfectly.

Rather than going to the trouble of trying to solder the whole thing together, why not cut off the nipple, fit a barbed union to the tap and join the petrol pipe up with a piece of rubber petrol hose and clips. That will also give the advantage of a little bit of flexibilty in the pipe and allow for any movement occasioned by your rally driving techniques.

regards

Barry R.