The 'E' Type Forum

About 2.5 years ago, I replaced the plastic tubing I had used as fuel hose on my MGB ( which uses about 3 feet of it ) with the proper, fabric braided and DIN certified stuff DIN 73379 , at not inconsiderable expense. Yesterday I found fuel leaking from it at various points, and further investigation shows that the hose has perished along its entire length . If you are using similar stuff, watch out, because the braiding conceals the dramatic deterioration of the rubber

Exterior view:


Underneath the braid:

Ethanol?

Well, I would hardly have thought so because you would imagine that the DIN certification would cover that . I must have a look at DIN 73379 and see what it says

Had the same with brake fluid...
Any known good source for reliable transparent fuel hose nowadays?

Ah, yes, the problem of osmosis with brake hose is now well known and a very great nuisance. It has been reduced, but not completely eliminated , with the pale blue expensive German stuff which I get from Hutsons

Not wanting to quote the entire DIN standard, but here are the appropriate highlights

Application area
Engine construction, Automotive engineering, Refrigerator technology, Mineral oil industry, Plant construction, Chemical engineering, Process engineering

Product specification
Fuel resistant chemical and hydraulic tubing according to DIN 73379
Resistant to fuels, fluids on mineral oil and glycol base, lubricants, animal oils, silicones, cooling water as well as diluted acids and alkalis at room temperature.
Good abrasion resistance
Good resistance to aging

Technical specification
Material: NBR (butadiene-acrylonitrile-rubber)
Temperature range: -40 to +90 ?C, for a short period +120 ?C
Medium temperatures:
Fuels: +40 ?C (benzene content up to max. 50 %)
Premium fuels: +40 ?C
Diesel fuels: +80 ?C
Universal fuels: +40 ?C
Cooling materials: +90 ?C (glycols, glysantine etc.)
Resistance to cold: -40 ?C
Max. operating pressure: 15 bar at +20 ?C

Just wondering, it there any chance of this being grey-market copy / pirated stuff from (say) China. Just because the machine prints DIN on the wrapping doesn't neccessarily mean that it is 3rd party analysed and verified as being the real-deal. If they can copy Rolex and I-phone then they can copy rubber hosing.

No matter - thanks for the warning / tip-off !

No mention of ethanol.

I was too quick there. Thanks David for spotting the missing word.

I have done a new search and found that DIN 73379 Type 3E is the spec for fuels containing ethanol. Also SAE 30R6 comes up as the ethanol compliant spec.

Here's some links to suppliers

http://www.advancedfluidsolutions.co.uk ... s-89-c.asp

http://www.veyance.com/ProductsDetail.aspx?id=6082

So why the deterioration in a safety related part? Makes you think the much maligned nylon fuel hose as originally fitted to the E-Type is actually a very good idea.

Well it deteriorates due to the alcohol (which is a solvent) reacting with the Type B syntethic rubber, whilst the others have a mixture that handles it.

Agree that the stiff nylon hose is probably not that bad a thing. Mine's certainly not coming off to be replaced with anything else. Which of course is even more true since it is a bugger to get off :D

If I remember correctly is there not a 1st year chemistry student out there somewhere. He can soon explain all the molecular bonding and reactions to us.

Heuer wrote:So why the deterioration in a safety related part? Makes you think the much maligned nylon fuel hose as originally fitted to the E-Type is actually a very good idea.

Rubber hoses deteriorate. I've removed and replaced the nylon stuff on several cars. The original does get hard and brittle but so have many of us after 50 years.

What did the inside of your hose look like?

No, something is amiss. There are millions of cars out there with rubber fuel hoses and there has been no safety recall. Either that hose was faulty or a fake with DIN markings - not unknown!

The original nylon hose is extremely robust and can hold all fuel grades without being affected, but it does get hard and brittle over time, and darkens in colour independently of the fuel contact. It is made of pure polymer, the wall thickness determines the overall properties, as well as the cost parameters.
Black NBR based hoses are produced out of a blend of NBR polymer with mineral fillers and carbon black pigment, somehow similar to a shoe sole. These can also be quite resistant to the variety of fuels, but their performance will depend much on the balance of the blend and particularly the porosity. The higher the NBR part, the lower the porosity, but also higher is the cost.
Kg to kg, it is way cheaper and faster to produce an NBR based hose than a Nylon one.

I agree with David : I think this was probably a fake of some kind . There was nothing remarkable about the inside, but then I could not examine it with a twist on it the way I did with the outside (I didn't bother cutting it open having seen the outside ) . I realise now, of course that there is virtually nowhere on an E type which uses this type of flexible tube, but for those who have other cars, it is quite common . Incidentally, there is a supplier who turns up at the shows who sells the nylon pipe in various sizes. The one point the lady who sells it makes with some force is that heat must NOT be used to get it over the fittings - use a lubricant instead