Replacing rusted out steel fuel line


My first time posting here and thank you in advance for any words of wisdom!

The 3/8” metal fuel line running under my S1 has sprung a leak and needs replacement. It is a long section running from just in front of the right rear wheel (where it is attached with hose clips to a 3/8” hose that leads up to the well), right to the front where it bends upwards through the front wheel arch (under trunking) to pass through side of the engine bay. I think at that point it connects to the line that takes fuel to the filter.

A lot of it is under trunking and heavily covered in underbody sealant - but I think the best thing is to remove the whole section, use it as a template to make a new one with nickel copper tubing, and refit without adding any more joins.

I haven’t removed the trunking/cover in the wheel arch yet but am expecting to see some type of 3/8” UHF 24 union…?

I have researched bending and flaring the tube which doesn’t seem too difficult (famous last words…). But I cannot find any information about how to make the unions, either to hose (at the rear) or to a connector (if, as I suspect, it joins another metal line where it passes through the wheel arch).

What ‘should’ these unions be? Can I attach the hose at the rear straight over the pipe and use 2 clips…? In which case would I still need to put a flare in that end, and what type?Or should I use some type of connector, in which case what - how do I attach the metal pipe (which I’d presumably need to flare), and how do I attach the hose?

And at the front, I am anticipating that when I remove the cover there will be a 3/8” UHF thread - and that I will join using a flare and a nut (presumably the female 3/8” fitting)?

Sorry if this makes little sense. I don’t know what I don’t know here, so there is no danger of patronising me if you state things that are obvious to everyone else! :grin:


Welcome on board, Adrian…

There is the chance that someone has the relevant parts catalog and can share the relevant drawing - eliminating some doubts. You can then decide which section is best replaced, copied if not available - and you may approach a hydraulic shop for professional work.

That’s the best I can do…:slight_smile:

xj6 85 Sov Europe (UK/NZ)

Hi Adrian…where are you located Automec in the UK have a good site for all fittings pipe kits etc…here are a couple of photos from the S2 parts catalogue…so should be similar…the hard steel line where it connects to rubber have a moulding on the end very much like an in built olive then a fuel clamp to the rubber hose…a double flare on the end of cunifer (copper/nickle) then pushed into the hose and fuel clamp would be suitable in my opinion…think your fuel pipe will be 5/16in…make sure you use ethanol proof hose…Steve
Brass Fuel Fittings (UNF) – Automec

Thanks Frank, thanks Steve. That’s really helpful. I am going to start stripping off the trunking and when I have seen the unions I’ll have a better idea of how difficult it might be. I may post a couple of pictures too.

I appreciate it,


Add images

I have got the cover off that protects the fuel and brake pipe work within the wing. It was simple enough once I realised flathead screws were buried in the chassis sealant.

So I have a length of rusty pipe, attached to the hose as shown at the rear right corner and to a metal union at the other end where the fuel supply passes through the inner wing and into the engine bay.

At one end I need to make a metal to hose connection. I assume I flare the nickel copper pipe and use a fitting that has a smooth bore section, onto which I can clamp the hose with high pressure clamps (not the worm drives as currently).

And at the other end I flare and will have a 3/8” nut/female, that I screw onto the 3/8” male thread that I imagine comes through the inner wing…?

I’ll look at the company you have mentioned for suitable fittings when I have dismantled and removed the old pipe.

Thanks, any other suggestions welcome!

The cover in the front wheel arch…

The cover removed…

1 Like

The line as it leaves the wheel arch… (close-up)

The other side of the inner wing, showing pipework to fuel filter.

Steve, I had one more question…

I understand what you are saying about the pipe/hose union. Flare the pipe; put ethanol-resistant 3/8” hose over it; clamp firmly with 2 clips.

I am dubious about disturbing the union at the inner wing. I don’t understand what fitting it is.

As the pipe towards the front of the car is good, it may be simpler to cut there and attach old to new pipe with a coupler.

I have looked at the Automec site and I can’t work out what I need. I think I am making a compression fitting, but the new pipe will be flared so no olive is needed. But unless I can flare the old pipe on the car (I have yet to flare so don’t know how easy or hard that would be), I would need an olive on the old pipe…?

And presumably I need a 3/8” male coupler, and 2 nuts on the pipes to make the join?

I think I am making this overly-complicated, have I got the right idea?!


Hi Adrian…making flares on old steel pipe on the car is very difficult if youve never done it befor…and useing a cheapish tool rather than a profesional expensive one even more so…far easier to cut the pipe and fit an olive and a compression fitting…are you UK or US…if uk then easy to call Automec and discuss. …or measure your pipe do a simple drawing of what you want to connect and we can try to help with what fitting you need…Steve

Thanks - that all makes sense. On that basis I am not going to do anything that involves flaring old steel. Flaring kunifer on a bench should be manageable from what I have read.

The temptation is to use penetrant on the union at the front end and separate the pipe in its entirety that way, as then I am not adding any new joins. My last photo shows the connection in the engine bay (the fuel pipe is beneath the brake pipe). The penultimate photo shows the pipe as it goes through the inner wing. I have cleaned it a bit and it is a brass fitting, but it doesn’t seem to be a compression fit - whatever thread is attached to it (presumably 3/8” UNF) seems to be brazed/welded.

I need to decide either to leave well alone and put a compression joint in on a straight section underneath. Or try separating the joint passing through the inner wing and when I have a better idea what I am dealing with, speak to Automec about suitable compression parts - provided the end of the pipe in the engine bay is already flared (and given I can flare the new kunifer pipe).





With carbs, Adrian - the fuel supply is very low pressure…

xj6 85 Sov Europe (UK/NZ)

The clamps are much nicer though.

Any chance of a S1 being wrecked near you? You could both try disassembly on that and get the parts…

Thank you. Pleased that I am working on a low pressure system!

I may be brave today and see what the fitting is at the inner wing.

I am surprised no-one else seems to have had cause to replace this pipe?

It is out in one section. The nut on the pipe to the fuel filter was not especially tight so as you say it must be a low pressure system.

The photo shows the end I have. I think now I need to flare both ends of the kunifer (a single on the hose end and a double at the front); and use a male in-line coupler (3/8” fine thread) with a female nut on the new pipe (and using the existing nut and flare on pipework in the engine bay)…

Here is my two pence!!

I have seen several videos on You tube. Stee fuel and brake
line repair in the rust country. Not uncommon. Compression fittings frowned on. I get it. All are EFI vehicles/ High pressures!!

Nevertheless., in my view, I am eith the flare fittings. Mainly as to the electric pump over mechanical.

The simlist of the fl;aring tools can be used on the car.

Then a mqeans of hoose to replace the rusted section.

Two means, in my view. Mate a barb to the steel. Very soleid anddoable.

Or a bit nore sophisticasted. I think a tool is available to form an olive on steel/ That and either form of clamo is just fine.

I made all the fuel lies on my Hot rod projet from steel lies. Simple double flare at each union.But, I found a hose that made the last part., chassis to carbs.

Ahh, and the Minnesota rubber line, held up with 3 strategically placed zip ties?

The pressure is a few psi, alternatively ~70 kg of fuel wanting to escape, maybe a little more when it warms up.

The no-flare brake line connections are illegal here, but that’s for brake lines. Maybe that is easier but a simple flare and a few fittings is easy enough.

Makes sense, David - brake line pressures are sky high…

xj6 85 Sov Europe |(UK/NZ)

Maybe 80 bar or so, like the power steering, but it’s not the reason why only flares are allowed- flares are seen as safer (and whoever does brake lines shouldn’t take such shortcuts)…