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Thread: Gas Tank Leak??

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    Registered User MidLifeCrisiz's Avatar
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    Default Gas Tank Leak??

    Daydreaming a little last night while pumping gas and filled my '71 right up and into the filler neck. Haven't had the car that long and guess never pumped that much gas in before, usually just pumped $20 worth or something. I have it running well and looking good so I pumped approx. 11 gallons last night. Stopped it just short of overflowing the filler neck by the gas cap. I then realized I had fuel pouring out over the top of the tank itself as though there is some type of vent on the top of the actual tank? The tank leaked itself down to a point that no additional dripping occurred, I dried everything off and let it evaporate for 30 minutes before starting the car. Probably let what seemed to be a 1/4 of a gallon of gas spill onto the pavement at the station. There goes $2.

    There seems to be no leak in the tank itself as it is holding on Full and no additional drips on the cardboard I put under in the garage last night. Drove it home 15 miles from the station and I can see fuel right up to the bottom of the filler neck with a flashlight beam.

    My question...do I need to investigate a leak right at the connection point of the filler pipe and the tank or is there some type of vent in the top center of the tank to handle this type of overfill situation? The gas seemed to be coming from the top center of the tank and running around all four edges as opposed to right from the neck area on that side of the car. The concrete was very level where I was filling up. It is obviously almost impossible to get your arm up and feel the top of the tank without lifting the car.

    Any help would be appreciated.

    Thanks
    Steve

    HLS30-24574 3/71 and donor HLS30-124816 9/72

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    Bitten by the Z bug hard bigoak's Avatar
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    Take a pocket digital camera and try to get shots of the top of the tank. Note this thread where I had an issue: http://www.classiczcars.com/forums/s...ad.php?t=26398

    Did the spill come from one side in particular?

    Given the rate of pouring out, I'd assuming you're missing something like the vent hose.
    Bigoak

    '71 240Z
    '77 280Z
    '87 300ZX

  3. #3
    Mike B
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    Quote Originally Posted by MidLifeCrisiz View Post
    Probably let what seemed to be a 1/4 of a gallon of gas spill onto the pavement at the station. There goes $2.
    Gas is $8 a gallon in Wisconsin these days? Yikes!!

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    Registered User MidLifeCrisiz's Avatar
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    BigOak,
    Good idea tomorrow I'll try and snap a picture of the top of the tank. The leaking did NOT seem to come from one side but rather directly out of the top center as it was running down and around all four sides of the tank. As opposed to where you showed in the photos on your old thread where you showed rust or corrosion on the connection seam on the tank between the top and bottom half of the clam shell...that is definitely not where my leak was occurring. It was running down off the top of the tank. I haven't had any fuel smell issues with the car and it sits in the same 3 car garage with my everyday boring to drive vehicles and the kid's bikes. I think I would have smelled it if I have a missing vent hose, never had it sitting with this much gas...maybe only a 1/2 tank but maybe we'll see more with pixs.

    Mike,
    NO Wisconsin gas even with our huge taxes is not $8/gallon. I believe the premium I pumped was $4.19/gallon down about $.40 in the past week that is why I pumped that much to begin with. I started thread by writing that I had spilled a 1/2 gallon and decided there was no way that much was spilled. Didn't adjust the math when I changed the amount to 1/4 gallon.

    Anyway...more to come with pixs. Thanks for the start.

    HLS30-24574 3/71 and donor HLS30-124816 9/72

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    Bitten by the Z bug hard bigoak's Avatar
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    Mine was only an issue when filled up completely...If i ran at 1/2 tank, never an issue.
    Bigoak

    '71 240Z
    '77 280Z
    '87 300ZX

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    beandip beandip's Avatar
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    you have the back top vent leaking. Your tank has a few vent lines that terminate in a evaporation tank located on the passenger side to the rear of the wheel. The vent hoses enter the cabin behind the plastic panel below the rear hatch , and travel to the area next to the filler neck. To do a repair the tank must be dropped and the hoses replaced. If you do not use OEM parts , be sure the hose used is rated for GAS . DO NOT be tempted to use heater hose. Napa has 5/8'' gas rated hose. If you do a search you will find a lot of information in this area. Gary
    I'd rather die while I am living than live while I am dieing. CZC 1887 IZCC 12602 Member of NorthWest Z Car Club

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    Registered User blue 72's Avatar
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    I think beandip is on the right track. I just had my gas tank out and back in this week, and there are two vent hoses on top, one on the driver's side, and then the fuel feed and return lines (mine's a '72). I've had this problem in the past, but now I know for a fact that everything is tightened down securely and not corroded or worn through. You only loose a few hours to check it (so many connections to remember and detach/hook back up). Plus, I got to fish out all the odd debris in my tank at the same time.
    '72 240Z - F54, P79, '78 5 Speed, 3.9 R200

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    Bitten by the Z bug hard bigoak's Avatar
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    If you are dropping the tank. Consider getting it cleaned and coated. Either take it to a rad shop or use the POR-15 kit.
    Bigoak

    '71 240Z
    '77 280Z
    '87 300ZX

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    A bit off-topic, but do they make new filler necks/hoses/grommets for the 240? My 240 leaks when I put fuel in, but not afterwards. Granted it was only a few gallons I put in. I figured there was a rubber filler neck hose or connector of sorts that might be leaking.
    http://www.classiczcars.com/forums/image.php?type=sigpic&userid=15572&dateline=1201351001

  10. #10
    Registered User MidLifeCrisiz's Avatar
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    Default Gas tank leak update with pics

    OK got the car slightly elevated and stuck the camera up and under. Based on feel for moisture (gas) and photos it is pretty obvious that the braided line directly above the gas level gauge on the passenger side is the culprit. This braided line runs up toward and next to the filler neck. Seems that I could get up and disconnect on the tank end...where does it go after it heads over by the filler neck? Is this the same line that ends up in the filler neck that you can see when you open the gas cap or goes to an evaporation tank? Has anyone replaced this line without dropping the tank?

    beandip...
    your comments about the evaporation tank...where is it located? Is it above the hatch deck in the quarter panel so I can access by removing the interior plastic or do I get access from underneath the car? Don't want to pull the interior apart just to investigate. This leaking braided line goes up and toward the passenger side as you described, but seems I could replace without dropping the tank. I can access the hose clamp connection on the tank without dropping it.

    Does anyone believe this isn't my issue? You can see from the pics that the line is wet where it connects to the top of the tank. I assume that this line isn't supposed to be porous but rather braided for flexibility...correct?

    bigoak...Thanks for the help and the idea about using the camera.

    Learning something new every day...better than a day in the office!

    thanks
    Steve
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    HLS30-24574 3/71 and donor HLS30-124816 9/72

  11. #11
    Mike B
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    Quote Originally Posted by Force Fed View Post
    A bit off-topic, but do they make new filler necks/hoses/grommets for the 240? My 240 leaks when I put fuel in, but not afterwards. Granted it was only a few gallons I put in. I figured there was a rubber filler neck hose or connector of sorts that might be leaking.
    It looks like Courtesy Nissan still has the filler necks.

    http://www.courtesyparts.com/Merchan...de=17208-S3074

    For the hoses, search for a post Arne wrote up a post about which hoses are better to buy EOM and which can be replaced with non-OEM.

    -Mike

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    Her Majesty the 26th 26th-Z's Avatar
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    Hey MidLife!

    Your vent hose is broken and you pretty much have to drop the gas tank to replace it. The Evap stuff is behind the quarter panel over the passenger shock tower. When you drop your gas tank, look for manufacturer markings on the top of the tank. You may find something interesting. I can't believe there isn't a fuel system diagram posted in the archives. This problem has been discussed a million times. Very common problem.

    So how's Wisconsin? I grew up in Mequon. Go Packers.
    Enjoy the Ride
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    Registered User Bonzi Lon's Avatar
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    That is the very hose I had to replace this spring, easy with the tank out. Please post photo of any markings on the top of the tank. If you have your evaporator tank off of its mountings, there may be a mark on its backside, facing the quarter panel, like the one on the fuel tank.

    Bonzi Lon
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    Registered User MidLifeCrisiz's Avatar
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    Hey 26th-Z,

    Wisconsin is unbeatable at this time of the year. High 70's low 80's with low humidity. Plenty of fresh water lakes to boat, swim, fish. Can't beat it. I live in Manitowoc.
    Those Packers...don't know about the Favre situation...he may just end up down in your neck of the woods with the Bucs.

    Anyway back to the problem at hand. I don't understand why I need to drop the tank to fix this vent hose. IF I can access the fitting at the top of the tank and get the clamp off, can't I fish a new line in to replace it? What am I missing? Or does it look easier than it really is. You guys have experienced it so guess it "is what it is".

    Someone mentioned on another thread relating to smell/fumes that they had just blocked up some of their gas tank vents permanently. Is this a viable option. I just am not excited about dropping the tank. Too many other things I would rather work on right now. Maybe down the road someday, but preferably would like to put my time in on other things.

    Maybe I'm dreaming and this can't be quick fix?

    HLS30-24574 3/71 and donor HLS30-124816 9/72

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    beandip beandip's Avatar
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    If you all do a search there has been several times this has come up. I did an article on how to eliminate the evap tank entirely several years ago. I showed dogma how to do it when he came by my house and then he did a step by step on one of the threads. All these hoses and there connections have been discussed several times and how to either replace or in some cases eliminate them.
    Gary
    I'd rather die while I am living than live while I am dieing. CZC 1887 IZCC 12602 Member of NorthWest Z Car Club

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    beandip beandip's Avatar
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    Quote Originally Posted by MidLifeCrisiz View Post
    Hey 26th-Z,

    Wisconsin is unbeatable at this time of the year. High 70's low 80's with low humidity. Plenty of fresh water lakes to boat, swim, fish. Can't beat it. I live in Manitowoc.
    Those Packers...don't know about the Favre situation...he may just end up down in your neck of the woods with the Bucs.

    Anyway back to the problem at hand. I don't understand why I need to drop the tank to fix this vent hose. IF I can access the fitting at the top of the tank and get the clamp off, can't I fish a new line in to replace it? What am I missing? Or does it look easier than it really is. You guys have experienced it so guess it "is what it is".

    Someone mentioned on another thread relating to smell/fumes that they had just blocked up some of their gas tank vents permanently. Is this a viable option. I just am not excited about dropping the tank. Too many other things I would rather work on right now. Maybe down the road someday, but preferably would like to put my time in on other things.

    Maybe I'm dreaming and this can't be quick fix?
    To answer the question about reaching the vent hose on the top rear of the tank. there is only about 1 1/2'' between the tank and the rear valance. If you can replace this hose without pulling the tank you are a magician. Almost always this is the hose that is leaking.
    I'd rather die while I am living than live while I am dieing. CZC 1887 IZCC 12602 Member of NorthWest Z Car Club

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    Registered User MidLifeCrisiz's Avatar
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    Got it. I understand there is only one Houdini...even though he did come from Wisconsin.

    Thanks.

    HLS30-24574 3/71 and donor HLS30-124816 9/72

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    Registered User MidLifeCrisiz's Avatar
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    Cool Success with a few bruised knuckles

    UPDATE - I was able to get to access the leaking vent hose loosen the hose clamp and slide it off the tank. Pulled the rear inside tail light panel and interior quarter panel open and removed the other end from the evaporation tank without dropping the gas tank! Slid the old hose up and out from the top. Replaced by reversing the process. I bought an extra 6" of hose...glad i did as it would have been impossible to slide the hose through the metal frame of the car right next to where it connects to the top of the tank with the tank in place. I was able to re-route around the frame member and it is still tucked up and out of harms way. I wasn't able to purchase braided line, but it is fuel line so should be good to go.

    If I need to chase additional lines in the future due to leaks, etc...I'll drop the tank and re-route this vent line as it came from the factory.

    I'm very grateful for the advice and putting me up to the challenge.

    HLS30-24574 3/71 and donor HLS30-124816 9/72

  19. #19
    Registered User Curtis240Z's Avatar
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    Good job. You can replace all three vent hoses without dropping the tank. I have done it a number of times. Using OEM prebent hoses help quite a bit.

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