Stuck Fuel Return Hose Fitting
05-21-2008, 06:14 PM
#33
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05-21-2008, 09:44 PM
#34
Bill,
From your photographs you have not cut into the outside root diameter of the nipple, so you still have the original wall thickness of the nipple.
By grinding the thread, you have lost some hoop strenght circumferentially in way of the spherical joint sealing face, however when you reinstall with the new pipe and nut, the new nut will give you back most or or all of the circumferential strength, but at the same time the spherical sealing surface of the pipe will apply tension stress to the area where the cutting wheel has cut into the thread.
Is it possible to feather out any stress risers in area, that is make the ground out area as smooth as possible with no sharp edges. If this is possible I would then reassemble the joint using a good sealing compount in way of the threaded area. In my day we used a compound called "Stag" sealant the dried quite hard, but still able to remove the nut at a later date.
I fully recognise that it is a fuel line and it will be under around 3.8 bar pressure, so in the end it will have to be your call. Jim Bailey sounds as though he has the solution, a 2nd hand unit.
I know it is a little late, but there are special spanners for pipe nuts, they have a ring spanner end with a section cut out to slip over the pipe and then fit onto the nut, giving a better grip on the nut, 5 1/2 flats.
In addition there are nut splitters that can slip over the nut like a hook and at the top end they have the fine threaded bolt through the hook with a cutter end like a chisel. You put it in position and screw down and the cutter end will split the nut.
Tails 1990 928S4 Auto
From your photographs you have not cut into the outside root diameter of the nipple, so you still have the original wall thickness of the nipple.
By grinding the thread, you have lost some hoop strenght circumferentially in way of the spherical joint sealing face, however when you reinstall with the new pipe and nut, the new nut will give you back most or or all of the circumferential strength, but at the same time the spherical sealing surface of the pipe will apply tension stress to the area where the cutting wheel has cut into the thread.
Is it possible to feather out any stress risers in area, that is make the ground out area as smooth as possible with no sharp edges. If this is possible I would then reassemble the joint using a good sealing compount in way of the threaded area. In my day we used a compound called "Stag" sealant the dried quite hard, but still able to remove the nut at a later date.
I fully recognise that it is a fuel line and it will be under around 3.8 bar pressure, so in the end it will have to be your call. Jim Bailey sounds as though he has the solution, a 2nd hand unit.
I know it is a little late, but there are special spanners for pipe nuts, they have a ring spanner end with a section cut out to slip over the pipe and then fit onto the nut, giving a better grip on the nut, 5 1/2 flats.
In addition there are nut splitters that can slip over the nut like a hook and at the top end they have the fine threaded bolt through the hook with a cutter end like a chisel. You put it in position and screw down and the cutter end will split the nut.
Tails 1990 928S4 Auto
05-21-2008, 11:14 PM
#35
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I checked the mating surface of the fitting with the cut threads and it looks undisturbed. I cinched the FMU hose to it firmly, then removed it and checked the fitting mating surface again. It looks OK. When I get the replacement hose tomorrow I will hook it up to the FMU, completing the circuit, and energize the fuel pump for a leak check.
I wonder how the nut splitter would work with the nut on a hollow pipe as opposed to a bolt.
I have some of those wrenches but not a 19mm. Also, with the hose fitting, I'm not sure it would have cleared the obstructions and getting anything but an open-end wrench on the 17mm counter-hold looks obstructed.
Thanks for the tip on the sealant.
I wonder how the nut splitter would work with the nut on a hollow pipe as opposed to a bolt.
I have some of those wrenches but not a 19mm. Also, with the hose fitting, I'm not sure it would have cleared the obstructions and getting anything but an open-end wrench on the 17mm counter-hold looks obstructed.
Thanks for the tip on the sealant.
05-21-2008, 11:27 PM
#36
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A flair nut wrench wouldn't work on the cooler because it wouldn't fit over the 19mm nut on the line. A really dumb combination on the part of Porsche. Bill, I think I have seen some crows feet wrenches in your tools, and they are generally flare nut types. Don't know if you had 19mm though.
05-21-2008, 11:33 PM
#37
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I can only add too all the above is that I'd grasp the lower hose with the most perfect wrench...............that was they way the P guys attached it. The cooler is then held by any manner...............I'd also suggest go forward a hair then back.
05-22-2008, 12:06 AM
#39
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Bill, The pictures look like your using open end wrenches on the b-nut. What you need are b-nut wrenches. They are a hex shaped wrench with a notch to let you get it over the line/tube. They are available at Home Depot and of course Snap on and others. The b-nut wrench puts pressure on 5 of 6 flats instead of just the two of the open end wrench. I've found they will even work on b-nuts that are partially rounded from open end wrenches.
05-22-2008, 12:26 AM
#41
Reanimator
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Man, I'm too late to the party again. That's what I get for working so much. I had the same problem with this fitting; took me almost three weeks of playing with it on and off, used liquid wrench, wd40, and some other stuff my landlord mixed up (kerosene and some other stuff he says works real good). Sat and tapped on all sides of it for hours. Went out and borrowed snap on flare nut wrenches for a good fit. Still nothing. I don't like to go to the pro's with questions, feel like an idiot, but there's a shop across the street. Asked them. Heat gun. Then a blast of freon. Heat gun again. Blast of freon again. Hold big old red hot soldering iron onto the nut for about 20 seconds or so. Easy twist, then a little click, the SOB came right off.
05-22-2008, 03:33 AM
#43
Team Owner
Dang Bill I was also thinking that you could just cut the factory swage off of the line and put a new line on and leave the nut connected
05-22-2008, 03:51 AM
#44
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Bill, The pictures look like your using open end wrenches on the b-nut. What you need are b-nut wrenches. They are a hex shaped wrench with a notch to let you get it over the line/tube. They are available at Home Depot and of course Snap on and others. The b-nut wrench puts pressure on 5 of 6 flats instead of just the two of the open end wrench. I've found they will even work on b-nuts that are partially rounded from open end wrenches.
05-22-2008, 03:52 AM
#45
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Man, I'm too late to the party again. That's what I get for working so much. I had the same problem with this fitting; took me almost three weeks of playing with it on and off, used liquid wrench, wd40, and some other stuff my landlord mixed up (kerosene and some other stuff he says works real good). Sat and tapped on all sides of it for hours. Went out and borrowed snap on flare nut wrenches for a good fit. Still nothing. I don't like to go to the pro's with questions, feel like an idiot, but there's a shop across the street. Asked them. Heat gun. Then a blast of freon. Heat gun again. Blast of freon again. Hold big old red hot soldering iron onto the nut for about 20 seconds or so. Easy twist, then a little click, the SOB came right off.
