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Car Forum / Driving, Maintenance, Tuning / Maintenance and Repair / January 2007Getting fuel line compression fittings leak free
The FI return line attaches to the fuel tank with a 5/16" compression fitting that I can't get a good seal on. I even replaced the tube section and of course used a new compression sleeve. I've tightened it quite a bit, but it still weeps. It so little that it probably wouldn't matter if it were an external tank. However, this tank is mounted in the trunk (Boot that is-- it's an older Jaguar), and the fuel odor is a problem. Any ideas? Rule of thumb for tightening these fittings? TIA Ed > The FI return line attaches to the fuel tank with a 5/16" compression > fitting that I [quoted text clipped - 12 lines] > > Ed tried teflon tape? I know it's only supposed to be used with pipe thread fittings, but maybe it'll help. I hate compression fittings. Can you flare the line and/or just replace the section with an AN type fitting or even a pipe thread style, or even just rubber and hoseclamps? Ray > tried teflon tape? I know it's only supposed to be used with pipe > thread fittings, but maybe it'll help. [quoted text clipped - 4 lines] > > Ray Ray, Thanks for the reply. I always assume these fittings leak either where the compression sleeve contacts the seats, or where it contacts the tube. If it seals at these places no fuel can get to the threads so I can't see how Teflon tape around the threads would help. As far as replacement is concerned the issue would be at the tank. If there is a fitting that screws into a female compression fitting and presents a female flare at the other end, I would like to know about it. There is already a hose clamped joint involved here. The tube in question has the compression fitting to the tank at on end and a hose is clamped at the other. It is just about 6" long, having a bend a little past 90 degrees and a short straight section at each end. IOW, unless I want to remove the tank and have a tank repair shop replace the fitting, I'm stuck with joining something to that female compression fitting in the tank. Ed Should not use compression type fittings anywhere in the brake or fuel system, oe doesn't and they are not recommneded for field repairs either. >> tried teflon tape? I know it's only supposed to be used with pipe thread >> fittings, but maybe it'll help. [quoted text clipped - 32 lines] > > Ed Are you sure its not leaking along the tank seam? Those things are famous for that. [Heavily Jag scarred} :) > Should not use compression type fittings anywhere in the brake or fuel > system, oe doesn't and they are not recommneded for field repairs either. [quoted text clipped - 39 lines] > http://www.newsfeeds.com The #1 Newsgroup Service in the World! 120,000+ Newsgroups > ----= East and West-Coast Server Farms - Total Privacy via Encryption =---- > Are you sure its not leaking along the tank seam? Those things are > famous > for that. > [Heavily Jag scarred} :) Not the seam. That problem was on later models. I know it's the fitting because I can see the oily residue when I run it with a tankful treated with an engine deposit remover... Chevron Clean-up This tank was removed and RENEWed about 3-4 years ago. My thinking is they messed up the fitting. Ed Shep, This is the 1976 Jaguar, and the OE did have compression fittings. Other than that, I agree with you. Ed > Should not use compression type fittings anywhere in the brake or > fuel system, oe doesn't and they are not recommneded for field [quoted text clipped - 5 lines] > ----= East and West-Coast Server Farms - Total Privacy via > Encryption =---- > Thanks for the reply. > [quoted text clipped - 21 lines] > > Ed I am assuming the fitting is soldered to the tank? Is it a return line OR the main feed line? If this is a standard compression fitting with a ferrule that fits the tube and a nut which forces it into a cone under pressure you could do a couple of things. First would be to pull it apart, clean up the parts VERY well, and then install the tube into the fitting and tighten it into the fitting on the tank. Now pull it apart and take it to the bench without moving the ferrule on the tube. Then use some solder and a propane torch and sweat solder the ferrule onto the tube. That would stop any possible leakage between the ferrule and the tube. Between the ferrule and the fitting presents a different challenge. I would possibly use a piece of thin lead foil. punch a hole in it large enough to fit over the tube and smooth it over the ferrule, then tighten down the fitting to compress the lead into a seal. Or you could wrap a piece of teflon tape around the ferrule and use it as a sealing device.  SignatureSteve W. Steve, Thanks for the thoughtful reply. > I am assuming the fitting is soldered to the tank? Is it a return > line OR the main feed line? It's the return line. > If this is a standard compression fitting with a ferrule that fits > the tube and a nut which forces it into a cone under pressure you > could do a couple of things. Yes, that's the type. > First would be to pull it apart, clean up the parts VERY well, and > then install the tube into the fitting and tighten it into the [quoted text clipped - 8 lines] > could wrap a piece of teflon tape around the ferrule and use it as a > sealing device. Interesting ideas. Maybe that was what Ray was suggesting when I thought he meant Teflon tape on the threads. Ed > Steve, > [quoted text clipped - 28 lines] > > Ed I did. I wasn't expecting it to work because it's a real hack, but I've seen guys use sewing thread to seal a leaking brake line fitting before... I prefer to do it the proper way, but sometimes duct tape and bailing wire is the next best thing. Ray >> tried teflon tape? I know it's only supposed to be used with pipe thread >> fittings, but maybe it'll help. [quoted text clipped - 32 lines] > > Ed Based on results I've had stopping leaks with teflon tape, both Ray & Steve W. gave you some good, proven-to-work advice. That common solution offered is also easy to apply. Why not be gentle, clean, methodical, and try it? While the fittings are apart, you may use a wire brush (steel brush) on the male threads to gently de-burr any roughness that may be present. Keep in mind just what you said about where the leak seeps from--tape can be used to seal the end of the comp. sleeve that is collared by the female-threaded coupler as well as the male-threaded fitting. You should be quite pleased with results from the effort. HTH, enjoy that Jag., good luck, AND HAPPY NEW YEAR. s > Based on results I've had stopping leaks with teflon tape, both > Ray & Steve W. gave you some good, proven-to-work advice. That [quoted text clipped - 7 lines] > pleased with results from the effort. HTH, enjoy that Jag., good > luck, AND HAPPY NEW YEAR. s Thanks for the reply. So, the idea is to wrap the Teflon tape over the compression sleeve so as to have a layer Teflon over the tapered surfaces at both ends, as well a the male threads? Ed > > Based on results I've had stopping leaks with teflon tape, both > > Ray & Steve W. gave you some good, proven-to-work advice. That [quoted text clipped - 16 lines] > > Ed No, that will 'not' work and is a great way to introduce chunks of teflon to the system. Teflon tape is a 'lubricant', it is not a sealant. It's job is to make the threads slippery and then squeeze out of the way usually. It is great stuff when used right. When you put one or two wraps of teflon tape on the threads, it just lets the nut tighten tighter easier stopping most leaks. Teflon tape can interfere with the seal between the parts that are supposed to mate up. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > No, that will 'not' work and is a great way to introduce chunks of > teflon to the system. [quoted text clipped - 12 lines] > > Mike Mike, Now that you mention it, I've had plumbers tell me that too. It's awfully soft stuff, so that may be right. So, what should I do about my leaks? Ed > Mike, Now that you mention it, I've had plumbers tell me that too. > It's > awfully soft stuff, so that may be right. > > So, what should I do about my leaks? It isn't clear why you have a leak. Are you sure the female fitting into the tank is even a compression fitting? It seems odd that a compression fitting wouldn't be removable or replaceable. Are you sure what you are attempting to use as a female compression fitting is not in fact a female pipe fitting? If that were the case then the way it supposed to work is that a fitting with a male pipe thread and female compression fitting is supposed to go between the tank pipe fitting and the tube male fitting. If the female compression fitting is attached directly to the tank - How is it attached? If it is soldered perhaps the solder joint is what is leaking. Another possibility is you are using a ferrule that is too small so that the male bottoms out in the female before it gets tight. Another possibility is that the seat is damaged or cracked inside the female fitting. This last point gets back to my first point. It is not to difficult to ruin the female part of compression fitting by over-tightening - so it would be odd if there were no provision for replacing it if it becomes damaged. -jim > It isn't clear why you have a leak. > [quoted text clipped - 28 lines] > > -jim Jim, Thanks for your response. Let me address some of the interesting points you raise. It is indeed a compression fitting. I've owned this car almost since new, and bought it from original owner who had it serviced only at the dealer. Moreover, the parts book drawings show what pretty clearly is a compression nut on a tube with a compression sleeve. And, it shows no adapter fitting in between. Don't know why you would say a female compression fitting would not be replaceable. This one is welded/soldered into the tank. Is this uncommon? I see nothing wrong with that in principle, once the decision has been made to use compression fittings in the first place. I got a new compression ferrule and a new length of tubing. Are you saying there are different sizes of these thing? Perhaps manufacturing tolerance differences? I, too, am thinking (reluctantly) about a damaged female fitting. I was unaware of the possibility of cracking them, however. My thought was that the shop that did the RENU process ( a franchised tank sealing process) allowed some of the tank lining/sealing gunk mess up the fitting. Ed > Jim, > [quoted text clipped - 16 lines] > fittings in > the first place. The problem is obvious if it gets damaged it will leak and there is no easy way to replace it or fix it. As I said before usually a compression fitting would be designed so that it is replaceable because they are easily damaged by over tightening. If everything was working properly it should not take much tightening to get a good seal. > I got a new compression ferrule and a new length of tubing. Are you > saying there are > different sizes of these thing? Perhaps manufacturing tolerance > differences? Yes, there are many different manufacturers and you can get ferrules made of different materials such as nylon or brass. They also come in different shapes. It could look like a cone with a hole in it or 2 cones back to back or even a sphere. Did you buy the part at a plumbing store or from someplace that sells OEM parts? > I, too, am thinking (reluctantly) about a damaged female fitting. I > was unaware of the [quoted text clipped - 3 lines] > lining/sealing > gunk mess up the fitting. If you look inside the female do you see a nice smooth seat that the ferrule can seal against? Does tightening it leave any tell tale markings on the ferrule that indicate where the problem is? And there is the possibility that the leak is coming from where the fitting is attached to the tank. -jim > Yes, there are many different manufacturers and you can get ferrules > made of different materials such as nylon or brass. They also come [quoted text clipped - 5 lines] > sells > OEM parts? I got the new ferrule at an industrial hardware store. It looked to be of a little better quality than at Ace, but still a part made primarily for copper tubing. In my car the tube is steel. The ferruel is not a separately listed part from Jaguar. > If you look inside the female do you see a nice smooth seat that the > ferrule can seal against? It's just about impossible to look into it without removing the tank from the car. When the fuel gets low enough I'll open it up and try to look in with a mechanic's mirror. Also, I was thinking about trying to smooth the seat if I could figure out how to get to it. Perhaps have a machinist turn a cone on a brass rod the size of the ferrule OD and put some lapping compound on it. >Does tightening it leave any tell tale > markings on the ferrule that indicate where the problem is? The old one looked like the ferrule was cocked a bit instead of parallel to the tube, like the tube was not going straight into the female when the nut was tightened. I made up a new tube and was very careful to get it straight when I replaced it. I'll examine it carefully when I open it up. >And there is > the possibility that the leak is coming from where the fitting is > attached to the tank. I don't think so. Ed > > Yes, there are many different manufacturers and you can get ferrules > > made of different materials such as nylon or brass. They also come [quoted text clipped - 44 lines] > > Ed Maybe the ferrule is too hard for the application? It could be a 'high pressure' steel one where you could be needing a brass one? You still should hear the threads making a creaking noise when they come to final torque. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > Maybe the ferrule is too hard for the application? It could be a > 'high > pressure' steel one where you could be needing a brass one? It's brass. > You still should hear the threads making a creaking noise when they > come > to final torque. I'll be listening for that when I take another shot at the problem. The tank is still about 1/2 full, so I'll wait till it gets a bit lower before opening the connection. I've learned it doesn't have to be completely empty. Ed Ok, here is a thought.... A plumbers copper pipe cutter, the kind with a cutting wheel and rollers, has this arrowhead shaped blade on the back side that pulls out like a pocket knife blade. This tool is used to ream out the inside of the cut pipe because it dimples in when cut which causes water noises in the plumbing. When reamed properly fittings are silent. I think I would use this blade to ream out the inside of the gas tank fitting to make sure the coating isn't uneven causing the ferule to not seat square. Basically I would make a new seat for the ferule with this tool. Barring that I think I would give up and use a piece of gas line hose or the more common transmission line hose, cut off the tank fitting, cut off the line fitting and use the hose and clamps on it and be done with it. It is low pressure so a normal worm gear clamp will work, but they make better clamps with a closed in band for high pressure (FI engine) gas lines. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) > > Maybe the ferrule is too hard for the application? It could be a > > 'high [quoted text clipped - 13 lines] > > Ed > > No, that will 'not' work and is a great way to introduce chunks of > > teflon to the system. [quoted text clipped - 20 lines] > > Ed I recommend teflon tape on the threads, it is great stuff. It will normally let a nut squash the o-ring even. We use it in plumbing on most household fittings. You should actually hear the nut start to make a creaking noise as it gets tight enough. Mike 86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's Canadian Off Road Trips Photos: Non members can still view! Jan/06 http://www.imagestation.com/album/pictures.html?id=2115147590 (More Off Road album links at bottom of the view page) >> I recommend teflon tape on the threads, it is great stuff. It will > normally let a nut squash the o-ring even. We use it in plumbing on [quoted text clipped - 5 lines] > > Mike Mike, Thanks for that tip. Now, finally, I see a connection between tape on the threads and sealing at the compression sleeve: the lubricative (is there such a word?) properties of the Teflon helps in getting better contact between the nut and the sleeve. Ed |
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