question for plumbing gurus

Does the steel have barbs or a bulge at the end? Is it the type of Oetiker that wraps around 360 degrees or the type with two ears?

There are so many variables Nate that a good answer is difficult.

Is the steel line ribbed, bulged, or flared or have any other way keeping the hose in place? What is the fluid? WAter, air, oil, etc. Temperature changes? Expansion, contraction Reinforced hose? Nylon, steel, etc. Vibration? How many layers? Radial, bias, etc. What is the hose really made of? Buna S, etc. How much hose is jammed onto the pipe? Several inches? Are the Oetiker clamps the kind that are ear crimped or the other kind?

I would figure it would hold a few psi long term on a smooth pipe if there is no vibration, nasty fluid, etc. If the pipe is flared or barbed, then it should hold at least the recommend max working pressure of the hose. Good quality air hose is good for around 150 psi max working pressure. Same for SOME very good fuel hose.

OK, well I guess I will have to post specifics then.

I own an '88 Porsche 944. It's nothing special, it's just my car. Right now it's basically my girlfriend's occasional driver, as I have a company provided vehicle. I just took it to a very well recommended race shop for some repair work, simply because it is difficult to find a good mechanic that can work on a Porsche, I'm not sure why this is but it is. Anyway, he has done a preliminary once-over of the car and one of his "punch list" items was to replace a section of rubber hose. This is a line from the fuel tank to the fuel pressure damper on the engine, unfortunately from the factory it is one solid piece from the rear of the car all the way to the front. The hose section is swaged onto the steel line. The hose began leaking shortly after I purchased the car, this was actually discovered by a different mechanic who I took the car to for a timing belt replacement. That mechanic cut the swaged collars off and replaced the rubber with a piece of standard high pressure fuel injection hose, double clamped at each end. He basically said that this was not a good fix, that I should keep an eye on it, etc. and I have - this was three years ago and it is still working fine, although at some point I was going to replace it because he used worm clamps and I would prefer to have smooth fuel injection type clamps on there.

This new mechanic is basically telling me that in his opinion any repair of that fuel line is substandard work and he recommends replacement of the entire part. "fortunately" in his words Porsche has superceded the old one piece line with a multi-piece line, but "proper" replacement involves ordering all the new factory Porsche parts and replacing everything from the tank forward, which would necessitate dropping part of the rear suspension. This would be several hundred dollars worth of parts and close to $1K in labor (at his shop.)

I don't mind spending money to make a car safe, but when we're talking about a significant percentage of the car's value, I am tempted to look for more economical alternatives. I've found this kit after a web search:

also this one

I've been sent some better pics of the Rennbay kit and it appears to be 3/8" diameter Aeroquip hose.

The only issue I have with both of these kits is their method of connecting to the hard steel line. The Rennbay kit uses a standard high pressure FI screw-and-nut hose clamp, and i'm curious if it provides enough compression to really crank down on the Aeroquip hose. The Lindsey kit uses a compression fitting to attach to the steel line, which I also don't like. I had two thoughts:

1) buy the Rennbay kit and use an Oetiker clamp (or two?) instead of the screw and nut clamp. 2) buy the Lindsey kit and instead of using the compression fitting, actually cut back the steel line and flare the tubing for an AN tube nut and use an AN fitting from the hard steel line to the hose.

The steel tubing, after cutting off the factory swaged crimp collar and removing the factory hose, does have a pronounced barb formed in it to retain the hose.

Again, I'm not trying to be cheap, but at an estimated cost of $1200 I figure if I can fix it correctly with one of the methods above, even if I have to buy some AN plumbing tools, I'll come out ahead by investigating alternatives. (and then I'd have AN plumbing tools.)

Unfortunately, a leak at the connection where the hose connects to the hard line would be a serious issue, as that would basically mean that high pressure fuel would be spraying directly on the exhaust header (yes, they are tubular stainless not cast iron - so they are probably even hotter than normal exhaust manifolds.) So much for that vaunted Kraut engineering... I guess they didn't learn anything from the shitty fuel line design of the 914. So you can see if I am going to do something non-factory, I want to make absolutely certain that I am doing the right thing.

I believe the mechanic has a valid point that the current setup is less than desirable; however, economically it probably makes financial sense to just drive the car until it burns to the ground rather than pay him $1200 to fix it...

nate

Now this may seem like a silly idea... Could the steel line be double flared on car like a brake line after a brake line fitting is slid on to it and then an adapter used to go from the brake line fitting to whatever you need for a proper fuel injection hose? (provided such an adapter exists or you could have one machined)

That's exactly what I was thinking, except rather than using a 45 degree double flare I was thinking of using a 37 degree AN flare (because the Lindsey kit uses AN hose and fittings are readily available.) However I have my suspicions that a good hose with an Oetiker clamp would be perfectly acceptable and less work.

nate

For whatever reason it didn't register that what you were thinking was that close except for the special flare tool. If adapters exist you could avoid the extra tool though.

Just googling around, it seems oetiker clamps are acceptable for fuel injection system fuel line.

I'd trust that for carburetor pressure but not for fuel injection pressure. For that I'd recommend using a Ferrell and compression nut fitting to attach to the steel, then attach a barbed fitting to that for the rubber. Use the type of Oetiker that wraps around 360 degrees. I've had too many leaks with the other type that have the two ears. These fittings will add weight so make sure that it is properly supported.

Just doing the 1st step of a brake-line style double-flare yields quite a good 'barb' at the end of a steel line.

Running steel line with maybe just short sections of FI rated hose would be the best cheap fix.

The hot-rodders use braided-stainless covered FI hose, as well.

Dave

Right, that's about what's there now.

nate

I like your idea #2. Flare the line _if possible_. Put the nut on first! There could be problem though - steel tends to get brittle in the presence of hydrogen. You may be able to flare the pipe considering its age. Still, it is worth a try. If that does not work, then you clamp a hose onto the steel pipe - assuming there is some sort of bulge to keep the hose on. You may want to reconsider the type of clamp because they are designed to expand somewhat. Hopefully they will not expand enough to slide over the pipe bulge.

I can make a bulge with a double flare tool if it comes to that...

'nother problem with the flare idea. I was given a pointer to this:

which appears to be similar to the Lindsey kit but I've been told that this guy actually originated the kit. I've exchanged a few emails with him already and he seems like a good guy to deal with. He's telling me that the hard lines are 10mm feed and 8mm return; therefore it's iffy if an AN flaring tool's anvil would grip it properly. (I should have anticipated that they would be metric; I'm so used to working on Studebakers that I forgot that Porsches use these weird sizes for things.) I do however have a metric bubble flare tool and have found adapters for bubble flare to AN-6 in the Aircraft Spruce catalog. I have not, however, seen any female thread tube nuts for metric fittings, which is kind of key to this whole plan... Vic at Pauer seems to think that the compression fittings are fine, and certainly in theory they ought to work... maybe I should just use them, but put some red Loctite on the threads just for insurance that they won't vibrate loose?

The good news is, however, I've found an Aeroquip distributor that is - shit you not - less than three miles from my house. This makes me very, very happy and yet worries me because this could easily become an obsession (well, since I have to make a new fuel line for the Studebaker, I might as well make that all AN as well, y'see, and some braided stainless brake hoses might be nice...) I will definitely be checking this place out tomorrow morning.

nate

On the torqueless wonder car I had a rust pinhole leak in a 10mm steel section of power steering line. It was a line that would be a pain to replace and the leak was near an end and accessible for the most part. I adapted 3/8th in metric brake line to the task. Of course the 10mm stock fitting slid over the brake line replacement bit just fine. Took the

3/8ths fitting to work and the hole was inlarged to 10mm on the lathe. Slid that over the 10mm line flared it with the brake flaring tool for 3/8ths. Used a union to connect it to the brake line. Worked perfectly. Anyway.. to the point the flare on the 10mm steel line turned out fine with some minor defect but that was due limited space I had to work in. I couldn't square the flaring tool exactly perfect because of it. But it did grip the 10mm line fine as I recall. 3/8ths is less than a half mm smaller than 10mm, I would think that the clamping range for the OD on a flaring tool should have at least that much adjustibility. It also makes for little float for the part that goes inside the tube, but it may only take a bit of tape around it to make up the .5mm. Even as is, the worst is probably a couple attempts to make a good flare.

We use aircraft stainless hoses on our hydraulic and diesel equipment. Great stuff.

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Update: I checked out the store I mentioned in my post above this AM. It looked promising from the street, but when I walked in I found that the only person manning the store was an attractive female about ten years younger than I. I have to admit that that didn't give me a whole lot of hope. Well, I just asked where the AN adapter fittings were, and she handed me an Aeroquip catalog and pointed me toward all the fittings which were neatly arranged in plastic bins by part number. After about ten minutes of poking around I couldn't find anything that looked like it would work, so I came back to the counter and explained to her exactly what I was trying to do. Not only did she catch right on to the whole concept, but she apologized that they probably *didn't* stock a metric fitting that would work for me, CALLED THE OWNER OF THE STORE, who immediately called back and spoke to me about what I was doing, apologized that he was OUT OF TOWN and promised to start looking for what I needed on Monday and would call me as soon as he'd found something.

Dayam. I didn't know places like that still existed. I feel like I owe the girl an apology for my initial impression, even though I certainly didn't let on.

The store is Hi-Performance Hardware, on Washington Blvd. in Arlington, VA. Good peoples.

nate