BigD New Reader
3/4/11 7:12 a.m.

Short version: is it ok to use stainless steel braided "rubber" fuel hose or do they really ALL weep fuel vapor and eventually harden and crack, so Teflon hose is the only right way to go.

Long version:

I'm getting ready to put my fuel system in and it's going to use SS braided soft line in the engine bay and pump/swirlpot area, with new hard lines inbetween. I was all set to order when I started seeing talk about the "rubber" (in quotes since there's probably little resemblance to it chemically) lines weep fuel vapor, with some owners saying that they were losing their mind trying to find leaks, then they swapped the lines for Teflon and the smell went away. Yet others said to me that the rubber ones will harden after a year or two and be a possible source of a major fuel leak.

Even though the Teflon stuff is super expensive, I'm willing to go that route but this just doesn't make sense to me overall. Every OEM manufactured car has rubber fuel lines. How many new cars stink like gas and then leak fuel after 2 years?

Is this just an epidemic of the SS braided rubber fuel hoses? Or is it just certain brands? Like say, if I get Aeroquip's rubber SS fuel hose, will it do the same?

Thanks in advance!


BigD New Reader
3/4/11 7:13 a.m.

Sorry since I don't see how to add a poll, what I also wanted to ask is if you do use SS braided rubber fuel lines, in addition to any advice which would be greatly appreciated, please tell me if you experience the vapor weep phenomenon, and which brand of hose you have.

emodspitfire Reader
3/4/11 7:43 a.m.

Never saw any Vapor "weep".

However...I did have to replace a line from the tank to the carb after it had been in about 10 years. I don't remember that it actually dripped fuel, but it was damp along the full length. This was Aeroquip line, I think.


SVreX SuperDork
3/4/11 8:01 a.m.

How about standard high pressure rated rubber fuel lines with the decorative SS wrap?

Fuel lines aren't fuel lines if they leak, "weep", or deteriorate from contact with fuel.

I just pulled some rotted rubber fuel lines out of my '60 El Camino that the PO installed. The fuel had eaten through them. I think it was probably vacuum line, not fuel line.

Dr. Hess
Dr. Hess SuperDork
3/4/11 8:35 a.m.

I only use Russell brand braided SS lines for critical applications (anything with pressure). You pay a bit more than the bargain SS lines, but it is much better quality than some unknown brand. I would think, though, that Jegs' private label brand would be OK. But I'll just stick with Russell's.

Also, I have a HF "cable cutter" that is THE way to go on cutting that stuff.

BigD New Reader
3/4/11 9:02 a.m.

Thanks for the replies guys, please keep 'em comin.

Rog: thanks, I guess 10 years I could live with.

SVreX: I wish that were the case but unfortunately these are all explicitly specified to be fuel lines by the manufacturer.

Dr. Hess: Unfortunately one of the instances of this problem is on a friend's racecar, who blames it on his Russell lines. I wonder if his racegas has anything to do with it, he uses ms109. I would personally only trust Aeroquip or Earl's (esp the former, having invented this stuff).

Last night I also reread the plumbing section of Carroll Smith's Engineer to Win and he never mentions anything like this. The only time Teflon hose comes up is for extreme pressure lines like brake and power steering... so confused.

Kendall_Jones Reader
3/4/11 9:21 a.m.

I'm a teflon user - on brake lines, fuel lines & oil lines. I hate the rubber stuff, especially now that Summit, etc have chinese knock offs. I've seen improperly installed aeroquip oil fittings fail at mid ohio with catastrophic results. Blew the hose off the connector.

I get my SS teflon hose & STEEL ends from mcmaster carr (or earls / aeroquip / russells all carry teflon as well). I like the way the Steel fittings with ferrules go together. And yes, I use steel ends cause I like em.

Here is a good tip if your braided lines are exposed to debris (and will cause them to fray). When you assemble the hose put heat shrink tubing over the lines for protection - works great, the f1 guys do it as well ;)


BigD New Reader
3/4/11 9:41 a.m.

Thanks Kendall!

Yeah I'm looking at using the Aeroquip TFE hose, and their hose ends. The main issue I ran into was when I was setting up my fuel pump. It has a -10 feed and while my pump to rail will be reduced to -8, I wanted to keep the swirl pot->filter->pump -10. So I bought some Russell "power steering" TFE hose which is -10. Up to this point I thought that "teflon lined" just meant a teflon lining inside the rubber. Good thing I haven't bought a pile of the regular nut/cutter fittings! The only issue with that is that the only -10 TFE hose end I could find from the major players was Russell and they're 40 bucks a pop.

I've been ordering my pipes and couplers from these guys, and I noticed they also have TFE hose and hose ends now. Ordered a pair of -10 ends to see the quality. Not sure if I would trust their hose though (scroll down for fitting design and price):

As far as fraying, I hear ya and that's why I've decided to run hardlines from the pump area to the engine bay, with ferrule AN adapters. The braided lines are tough but I'm chicken.

wlkelley3 Dork
3/4/11 7:20 p.m.

Fuel rated rubber lines shouldn't weep, leak or anything else that lets fuel come out of places it isn't supposed too. Steel braided or not. The steel braid on the outside will let it last longer and take more external abuse (and look nice ). Shouldn't be any different than plain rubber fuel rated hose. That's all I usually keep around the garage. Although a bit more costly than plain rubber line, the advantage is I don't have to worry and can use it for just about anything. That said, teflon lines are nice although not as flexible. Should last the life of the car though. Or longer.

SVreX SuperDork
3/4/11 7:54 p.m.

"Weeping" fuel vapor sounds totally wrong.

I'm not getting this. Something is not right.

Liquid gasoline doesn't burn. It's the vapors.

It's gotta be bad fittings, or some other such thing. Leaking vapors would be explosive. It can't be normal that fuel rated lines allow fuel vapor to "weep".

BigD New Reader
3/4/11 8:07 p.m.

I wish it were so. There are literally dozens of threads out there, people losing their minds with high dollar, big power builds using top of the line components and smelling like gasoline. Some of the earlier ones end in having a chemical sniffer determine the source of the vapor - and it's the lines. Other people are told to try changing the lines and the smell goes away.

I was hoping that I could find some kind of catch but I've asked this question in many places, and everywhere else I've been told that the problem is real. One racer even told me that the fuel smell is just part of the experience... no thanks. Another long time dragracer said that the neoprene liner of the rubber SS lined fuel hoses deteriorates over the span of a few years and can lead to a serious fuel leak.

Sample search results (woo I made the list):

porksboy SuperDork
3/4/11 8:49 p.m.

Dr. Hess, do you have a link or pic of the HF cable cutter?

As for protecting the steel braid use the clear vinyl hose that is available at the hardwear store. Allows you to inspect the braid underneath.

Brotus7 Reader
3/4/11 9:18 p.m.

I've had SS braided lines on 2 cars, and with 2 different results.

I had a set on my Digi 1 GLI and that car always had a fuel vapor smell under the hood, but never any leaks. Earl's line and fittings.

I have a set on my MR2 now and I have absolutely zero problems. Summit lines and fittings.

I think the difference is how I put it together. The second time around I used my angle grinder with a cut off wheel to make a quick, clean, straight cut and then the fittings popped on with no drama. The first go around on my GLI wasn't so simple. I tried using the tape and saw technique but what a royal pain in the ass that turned out to be for me.

BigD New Reader
3/4/11 9:21 p.m.

Yeah this is my first time making these kinds of hoses and already to me none of the methods make any sense besides the cutoff wheel - especially the cutters or the chisel method, both crushing the hose. I realize that it's probably fine but it just doesn't seem right.

mike Reader
3/4/11 10:13 p.m.

Not sure this will add to the conversation, but here goes nothin'. I've worked with braided hose for, oh, about 25 years now, and over that time i've become somewhat of a snob about such things. For user-assembled hose, I really only go with ptfe-lined hose, and I greatly prefer the hose with a non-abrasive, low-friction overbraid. I lost a race once because a piece of gravel got between two oil cooler hoses, and one hose sawed the rock against the other until the hose popped (and yeah, I was leading dang it!). Not to mention the number of times I have found the end of a braid wire with the side of my hand as it gave me a solvent "injection". Ow.

Anyway, I prefer Aeroquip, XRP, or Earl's hose - something name-brand, anyway, and generally (much to my chagrin) more expensive.

9/7/11 6:58 a.m.

Hi Guys,

Just found this post and wanted to add some info we at TechAFX have learned in doing AN PTFE fuel hoses.

First of all, if you are using PTFE (Teflon) hose to transfer fuel, you need to make sure the hose has a 'conductive core'. This is easily recognized as the inside diameter of conductive core hose is black--vs the off-white color of 'non-conductive core' PTFE hose. This is important as fuel is a non-conductor AND it generates a static charge as it passes through PTFE hose. The black color in the PTFE conductive core hose is actually carbon--which allows the static electricity to pass through the hose/fittings assembly to ground. Without that, the static charge builds in the hose, looking for a path to 'ground' to--not a good situation. All PTFE fuel hoses used on production cars are conductive because of this issue--TechAFX only offers conductive core PTFE AN hose.

Second, the reason rubber hoses are failing now is because the chemicals/additives being used in today's fuel are not compatible with rubber hose. The production car business has not used rubber fuel hose for over 10 years because they were aware of the issues with being able to handle these fuels--the aftermarket is just now realizing how serious this issue is and that the only solution is PTFE, conductive-core hose.

I know because TechAFX has been doing extensive development/testing in an SAE-certified lab of our PTFE hose assemblies vs rubber hose--and the results are dramatic. To see some of these results, check out the January 2011 issue of HOT ROD magazine...they used some of our testing results to support a story called 'When Good Hoses Go Bad'. One of the results of this work was the release of our affordable, home-assembled PTFE, conductive core AN hose and fittings line.

We had not planned on getting into this business--we are primarily a provider of OE-style QD fitting performance hose assemblies--but we felt a cost effective PTFE hose solution was needed based on our testing results, so we created an AN PTFE hose/fitting product line.

We believe fuel transfer requires the utmost in safety.

I think most of us would agree this side of the business saw almost no requirements change for many years. But it seems to be experiencing a dramatic shift in the requirements now--we believe the solution is conductive-core, PTFE AN hose.

Hope that helps

Giant Purple Snorklewacker
Giant Purple Snorklewacker SuperDork
9/7/11 7:17 a.m.

I treated mine like a brake system and ran steel hard line everywhere but the last 3 inches to/from the fuel rail to keep engine vibration from fatiguing the line (even though it is solid mounted). The last 3" are high pressure OE production fuel line from an E92 M3 I had laying around. Not nearly as sexy as all that SS with blue and red anodized fittings... but no leaks. No weeps. Bonus... steel is a conductor!

6/29/13 2:08 p.m.

In reply to BigD:

The problem with rubber fuel hoses, is the fact that they are putting more and more ethanol in the rule. Ethanol is an alcohol based liquid. So therefor it will after awhile dry out the rubber. What actually happens is that the alcohol reacts to the rubber drying out the elastomers, thus the hose becomes britlte and eventually cracks, thus emits fuel vapor. If you use swivel hose hose end that have has an o ring in it. It could also be affected by the ethanol, so depending on the rubber compound you have an issue, it does not always happen right away. As far as rubber goes, their are companies that make great SS braided rubber hose. it is just difficult to make a rubber based product that will take alcohol for ever. So if you want to be sure, teflon hose is your best solution, using a teflon hose end that either does not swivel or one that uses a pin to secure the end fitting to the tube. This style have been around for quite a awhile. As long as you use a good quality teflon hose, you should have no problem. As for ultimate protection you can use a teflon hose that has a carbon tube, this allows the hose to grounded, so that no static discharge can affect the hose. This is not always necessary, it has to do with how flow and pressure that will create a static buildup.

Stuart Techna-Fit, inc.

shadetree30 Reader
6/29/13 2:52 p.m.
Giant Purple Snorklewacker wrote: from an E92 M3 I had laying around.

I so hate you...

Datsun310Guy UberDork
6/29/13 3:20 p.m.

In reply to Will_TechAFX:

I sell Teflon braided hoses for industrial applications - all your comments are spot on. Great advice.

If conductivity is an issue - you do want the black (carbon black) Teflon - it cuts down on static.

44Dwarf SuperDork
6/30/13 6:39 a.m.

I've never seen rubber SS hose weep fuel an I’ve seen lots of injected race car running it for 12 feet or more. HOWEVER I will say I've also seen a lot of these same cars suffer from clogged injectors as most didn't put the filter near the rail. Me personally I take the NHRA approach and anything over 15 inches gets hard line and I use the Teflon line for any flex sections as it is chemical safe for anything the government desires it want to put in fuel....put a large filter as close to the rail as possible and use SS hard tubing (cleaned and caped) never a problem after that. Cost more yes... no more clogged injectors... finishing races PRICELESS.

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