My 1992 Hunter Legend 37.5 has a Yanmar 3HM35F diesel that has always leaked a few drops of diesel fuel at the "banjo style" fuel line fittings on the fuel filter housing. The problem seems to be that Yanmar uses copper washers as gaskets on these "banjo" fittings. They stay tight and dry for about four or five uses of the engine, but they loosen. I've replaced the washers with new "Yanmar issue" washers. I continued tightening the fitting until the threads finally stripped out of the fuel filter housing (so I had to buy a new one for $50). This problem would be devastating if it were a gasoline engine (i.e. explosive fumes from raw gasoline in the engine sump pan.) With the diesel fuel it is more of a niusance than a safety issue. About 5 drops of diesel fuel leak out of these fittings into the engine sump for every engine hour. It also makes the cabin smell like diesel fuel. I've looked at my friend's 1996 Hunter Legend 37.5 and found that he has a different Yanmar. The fuel filter is up on top away from the heat of the engine block and has a large spin-on fuel filter instead the small insert type filter that I have. There is no fuel leakage from his filter fittings. I consulted one Yanmar diesel mechanic and he advised that my model always leaks a few drops of diesel fuel from the fuel filter. I've lived with it for the last 750 engine hours, but it sure would be nice to get rid of this fuel leak. Any suggestions?
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My condolances
as I had exactly the same problem on a new Yanmar 2GM20F. The fuel filter is near the top of the engine and out in the open so it was easy to see where the leak was coming from. I removed the soft copper gasket from teh vent screw and carefully wrapped it with teflon tape taking great care not to force any part of the tape into the filter. The engine is now clean enough to cook on. Regards, s/v Island Hunter
as I had exactly the same problem on a new Yanmar 2GM20F. The fuel filter is near the top of the engine and out in the open so it was easy to see where the leak was coming from. I removed the soft copper gasket from teh vent screw and carefully wrapped it with teflon tape taking great care not to force any part of the tape into the filter. The engine is now clean enough to cook on. Regards, s/v Island Hunter
Pardon my "ignorance", what is a banjo fitting ?
I have read about them before and I've done maintenance work on my Yanmar engine a 2QM15. (no diesel leaks, BTW). Could somebody describe them. Thanks
I have read about them before and I've done maintenance work on my Yanmar engine a 2QM15. (no diesel leaks, BTW). Could somebody describe them. Thanks
fuel leak
I have worked with these "banjo type" fiitings before on gas engines not on diesels. Usually changing the copper washers does the trick, but I see not in your case. I would think the problem has more to do with vibration then heat. Is it possible to relocate the filter? How about upgrading your fuel filtration system to a Racor or comparable system? Chris
I have worked with these "banjo type" fiitings before on gas engines not on diesels. Usually changing the copper washers does the trick, but I see not in your case. I would think the problem has more to do with vibration then heat. Is it possible to relocate the filter? How about upgrading your fuel filtration system to a Racor or comparable system? Chris
Similar Leaks
My 1997 h340 has a 3GM30F which developed the same leak at the banjo bolts on the secondary fuel filter. BTW Tom, a banjo bolt or banjo fitting is a round fuel fitting with a bolt or screw through the center of it. It is sort of shaped like a banjo if you have a good imagination. There is a round part ttrhat the bolt goes through and the part where the fuel line comes off the filtting is like the neck of the banjo. I have seen these banjo fittings on automobile fuel systems as well on Toyotas and British cars too. The banjo's on my Yanmar are on the secondary fuel filter, my primary is a Racor mounted elsewhere. On my 3GM30, the secondary fuel filter is mounted on the side of the engine between the fuel pump and the injector pump / governor. I have had problems with these fittings leaking a few drops per hour as decribed by Don H. I sure like Ralph's suggestion of putting a layer of teflon tape on the copper washer. I have replaced the copper washers/gaskets in the past and have used up my supply. I went to buy some spare copper washers recently at my local diesel engine parts store and I was dissapointed to find that they no longer have authority to carry Yanmar parts. (I suspect that Yanmar is unhappy that this store carries other brands of diesel engines and has yanked their franchise for Yanmar parts.) The nearest parts store was now about 40 miles away and I was not happy about that.) The consumer loses! I snugged up the fittings and they don't leak for now and did not leak on my most recent trip when I put 20 hours on the engine. I am happy to hear about the teflon tape suggestion. Thank you Ralph!
My 1997 h340 has a 3GM30F which developed the same leak at the banjo bolts on the secondary fuel filter. BTW Tom, a banjo bolt or banjo fitting is a round fuel fitting with a bolt or screw through the center of it. It is sort of shaped like a banjo if you have a good imagination. There is a round part ttrhat the bolt goes through and the part where the fuel line comes off the filtting is like the neck of the banjo. I have seen these banjo fittings on automobile fuel systems as well on Toyotas and British cars too. The banjo's on my Yanmar are on the secondary fuel filter, my primary is a Racor mounted elsewhere. On my 3GM30, the secondary fuel filter is mounted on the side of the engine between the fuel pump and the injector pump / governor. I have had problems with these fittings leaking a few drops per hour as decribed by Don H. I sure like Ralph's suggestion of putting a layer of teflon tape on the copper washer. I have replaced the copper washers/gaskets in the past and have used up my supply. I went to buy some spare copper washers recently at my local diesel engine parts store and I was dissapointed to find that they no longer have authority to carry Yanmar parts. (I suspect that Yanmar is unhappy that this store carries other brands of diesel engines and has yanked their franchise for Yanmar parts.) The nearest parts store was now about 40 miles away and I was not happy about that.) The consumer loses! I snugged up the fittings and they don't leak for now and did not leak on my most recent trip when I put 20 hours on the engine. I am happy to hear about the teflon tape suggestion. Thank you Ralph!
Similar Leaks II.........
Have a 87' Legend 37 with the 3hm35F with the usaal pump/filter bolted to the side of the block. Vibration IS a key factor in the whole leak scnerio. The aft starboard motor mount was bad causing the engine to vibrate severely through certain RPM ranges. During this process the copper gaskets became causing the fuel to leak. Replacing the mount(reducing vibration) helped significantly. There were still a few drops (as everyone mentioned) and the dealer suggested coating the copper gaskets with a small amount of a 'liquid gasket' compound that is normally used on automobiles. This seems to work however, adding this and probably the teflon tape makes me a little nervous - in the event some breaks off and enters the fuel line. On te plus side, if it did, it would be trapped be the secondary filter. Haven't seen anything in this filter yet....
Have a 87' Legend 37 with the 3hm35F with the usaal pump/filter bolted to the side of the block. Vibration IS a key factor in the whole leak scnerio. The aft starboard motor mount was bad causing the engine to vibrate severely through certain RPM ranges. During this process the copper gaskets became causing the fuel to leak. Replacing the mount(reducing vibration) helped significantly. There were still a few drops (as everyone mentioned) and the dealer suggested coating the copper gaskets with a small amount of a 'liquid gasket' compound that is normally used on automobiles. This seems to work however, adding this and probably the teflon tape makes me a little nervous - in the event some breaks off and enters the fuel line. On te plus side, if it did, it would be trapped be the secondary filter. Haven't seen anything in this filter yet....
Before you check your washers...
...be sure to have spares around. Yanmar told me that these are "one time use" copper washers and should be replaced each time they are removed because they seat/shape themselves to the fitting.. I bought a package of 10 for $4 from yanmar. When I replaced the leaking banjo washers, the leaking reduced, but I still get a bit of leakage, even with the new washers.
...be sure to have spares around. Yanmar told me that these are "one time use" copper washers and should be replaced each time they are removed because they seat/shape themselves to the fitting.. I bought a package of 10 for $4 from yanmar. When I replaced the leaking banjo washers, the leaking reduced, but I still get a bit of leakage, even with the new washers.
Leak at Pump
Don, Similar problem. The fitting from the engine filter to the engine always seemed to leak. Changed the copper washers, tightened the fittings, thankfully didn't strip the threads, but nothing worked. Finally solved the leak by replacing the metal mesh hose between the filter and engine. Seems the rubber hose inside the metal mesh would leak under pressure. The fuel, couple of drops per hour, would run down inside the mesh to the fitting and appeared to indicate a leaking fitting. The metal mesh inself didn't hold the fuel long enough to indicate a leak and the leaking rubber hose underneath couldn't be checked. Think the hose cost about $10 and the time to replace was about 5 mins not including bleading the system and checkout. The engine has been completely dry (knock on wood) for about a year. Les sv Mutual Fun.
Don, Similar problem. The fitting from the engine filter to the engine always seemed to leak. Changed the copper washers, tightened the fittings, thankfully didn't strip the threads, but nothing worked. Finally solved the leak by replacing the metal mesh hose between the filter and engine. Seems the rubber hose inside the metal mesh would leak under pressure. The fuel, couple of drops per hour, would run down inside the mesh to the fitting and appeared to indicate a leaking fitting. The metal mesh inself didn't hold the fuel long enough to indicate a leak and the leaking rubber hose underneath couldn't be checked. Think the hose cost about $10 and the time to replace was about 5 mins not including bleading the system and checkout. The engine has been completely dry (knock on wood) for about a year. Les sv Mutual Fun.
Fuel Filter Design Flaw
The Yanmar Fuel filter is flawed in its design. Ultra soft metal in filter housing and washers that can only be used once before they deform aren't a good combination for a marine diesal engine. The assembly just begs to strip and leak fuel anytime that it is touched by human hands. I have seen thin nylon washers that replaced the copper washers on the infamous "banjo" bolts. I also try to NEVER touch the assembly, and to never use the bleed screws..EVER. I'm sure Yanmar knows this component assembly is poorly designed with feedback from many many mechanics and owners who have complained about the problem. Touch at your own peril!!
The Yanmar Fuel filter is flawed in its design. Ultra soft metal in filter housing and washers that can only be used once before they deform aren't a good combination for a marine diesal engine. The assembly just begs to strip and leak fuel anytime that it is touched by human hands. I have seen thin nylon washers that replaced the copper washers on the infamous "banjo" bolts. I also try to NEVER touch the assembly, and to never use the bleed screws..EVER. I'm sure Yanmar knows this component assembly is poorly designed with feedback from many many mechanics and owners who have complained about the problem. Touch at your own peril!!
The old banjo
There are lots of old banjo fittings out there that don't leak. The design doesn't change. The parts should be the same. The big variable is the installation. The use of soft copper washers is ubiquitous for this and many other applications. When properly tightened, the copper is compressed and should conform to the surfaces with which it is in contact. The process cold works the copper and takes if from soft to hard, ie: not reusuable. This would lead to the postulation that once a leak starts, retightening, without new washers, should not work. (From the posts I have read, this is confirmed.) Now to the installation. When tightening a banjo bolt, the inner washer gets pure compression while the outer gets compressed while undergoing some sliding motion, unless the banjo rotates as the bolt is turned. that would result in a combination of things. Any dirt, contamination or scratches on any of the surfaces can lead to a leak. When tightening the bolt, it is imperative that the fitting not rotate. Consider what is happening if it does. The tube is loaded up like a torsion spring (especially the rigid tubes). this puts a force on the bolt in the "lefty-loosy" direction. Start things vibrating and the tendancy is for the bolt to loosen - and it doesn't take much to let diesel fuel by. It would probably be a wise maneuver to displace and hold the tube in the direction against tightening rotation as the bolt is tightened. Ergo, the spring is loaded in the tightening direction. As is probably evident, this treatise is composed as the thoughts develop. I do not know for certain the real cause for those leaks but I do know that the majority of banjo fittings are tight. I hope that all this input will strike a spark that will come up with a conclusive answer.
There are lots of old banjo fittings out there that don't leak. The design doesn't change. The parts should be the same. The big variable is the installation. The use of soft copper washers is ubiquitous for this and many other applications. When properly tightened, the copper is compressed and should conform to the surfaces with which it is in contact. The process cold works the copper and takes if from soft to hard, ie: not reusuable. This would lead to the postulation that once a leak starts, retightening, without new washers, should not work. (From the posts I have read, this is confirmed.) Now to the installation. When tightening a banjo bolt, the inner washer gets pure compression while the outer gets compressed while undergoing some sliding motion, unless the banjo rotates as the bolt is turned. that would result in a combination of things. Any dirt, contamination or scratches on any of the surfaces can lead to a leak. When tightening the bolt, it is imperative that the fitting not rotate. Consider what is happening if it does. The tube is loaded up like a torsion spring (especially the rigid tubes). this puts a force on the bolt in the "lefty-loosy" direction. Start things vibrating and the tendancy is for the bolt to loosen - and it doesn't take much to let diesel fuel by. It would probably be a wise maneuver to displace and hold the tube in the direction against tightening rotation as the bolt is tightened. Ergo, the spring is loaded in the tightening direction. As is probably evident, this treatise is composed as the thoughts develop. I do not know for certain the real cause for those leaks but I do know that the majority of banjo fittings are tight. I hope that all this input will strike a spark that will come up with a conclusive answer.
I wish there was a "definitive answer"...
As ponited out, it is an endemically weak link in the fuel supply system. Nylon washers lack the proper compression. I'm leary of teflon tape on the threads although it often may work at first, but rarely for the long term. Brand new copper washers coated with a thin coat of fuel-proof gasketing material on both sides and suffucient torque to properly compress the washers (but not too much to deform the threads) has worked for me. (and as someone said, never touch them again, until you have to replace fuel hoses...)
As ponited out, it is an endemically weak link in the fuel supply system. Nylon washers lack the proper compression. I'm leary of teflon tape on the threads although it often may work at first, but rarely for the long term. Brand new copper washers coated with a thin coat of fuel-proof gasketing material on both sides and suffucient torque to properly compress the washers (but not too much to deform the threads) has worked for me. (and as someone said, never touch them again, until you have to replace fuel hoses...)
Definitive Answer Back Three Messages
Paul, You may want to check out the posting by Gordon Torreson (August 3) if you missed it. It appears that there are some ideas there worth exploring. After you have tried those things it would be great to hear about your progress. Joe
Paul, You may want to check out the posting by Gordon Torreson (August 3) if you missed it. It appears that there are some ideas there worth exploring. After you have tried those things it would be great to hear about your progress. Joe
Diesel Leak
Same identical problem on 2GM20. Yannmar won't admit problem but has a partial fix. They sell rubber coated washers. Also I found the hard tubing between pump and filter can be replaced with 1/4 fuel hose; ie John Deere yanmar tractor engines. fuel filter is larger banjo fitting and will require coating copper(new) washers and banjo fitting and hose barb! with liquid gasket material, double clamp hose in place and your home free. I have not had another leak from either end in two months.
Same identical problem on 2GM20. Yannmar won't admit problem but has a partial fix. They sell rubber coated washers. Also I found the hard tubing between pump and filter can be replaced with 1/4 fuel hose; ie John Deere yanmar tractor engines. fuel filter is larger banjo fitting and will require coating copper(new) washers and banjo fitting and hose barb! with liquid gasket material, double clamp hose in place and your home free. I have not had another leak from either end in two months.
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