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Tank sweat..? for Newbies

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  • Tank sweat..? for Newbies

    Opportunity is knocking on 2k contour, former state vehicle with bad t belt & 110k on the clock.(Winter project) while looking it over noticed tank sweating no smell of gas at all any insight as to why this is. {has been parked around three months}

    lease ran out on 98 long time back i don't recall this, but hey i did not have to work on it either..



    Regards:CL Dobbs

  • #2
    Re: Tank sweat..? for Newbies

    You say that the tank in a 2000 Contour is "sweating"? The Contours have a Type II tank (Steel with composite around the cylindrical section). Natrual gas does not permeate through steel, and even if it did, it would not "sweat" because it is not a liquid. You mention "winter project". Could it be that the "sweat" is condensation from cold temperature? I don't what else it could be.
    Jared.
    Mountain Green, Utah
    2003 CNG Cavalier
    2003 CNG Silverado 2500HD

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    • #3
      Re: Tank sweat normal..?

      Should Condensation be there @ an average of 54°F ambient outside temp ?

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      • #4
        Re: Tank sweat..? for Newbies

        Need more info than just the local temperature... with high relative humidity (a high dew point) and tank being cooler than 54 (could be from recent use... if you moved a significant amount of fuel out of the tank in a short period of time, the tank will get colder), you could easily see condensation. I've never seen any tank condensation myself, but then again, we don't really need rear window defoggers either (in the Phoenix area)...
        2008 GX (extended range, trunkless version)
        Polished Metal Metallic 2012 Civic Natural Gas
        Fuelmaker FMQ-2-36 (since 2001)
        Previously owned: 2000 GX (11 years), 1995 Bi-fuel Sonoma, 2000 Bifuel Tahoe, 2000 Bi-fuel F150

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        • #5
          Re: Tank sweat..? for Newbies

          I have a 2004 F150, dedicated CNG. It has 3 tanks: 2 in the bed behind the passenger compartment, and 1 underneath the bed.

          The tank underneath the bed is mounted longitudinally (i.e. the length of it runs parallel to the drive shaft and exhaust tubing). There is heat shielding around this tank.

          If the vehicle is completely cold (first start in the morning, but I'm in CA so it's never been colder than 60 degrees outside) and I drive a short distance and park... when I come back to the vehicle I have a puddle of water under the vehicle and water dripping from the general area of the under bed tank.

          I've never gotten under the vehicle to look (have either been in a hurry or wearing good clothes), but my theory is that the heat of the exhaust in proximity to the "cold" under bed tank causes condensation on the exterior of the tank.

          Don't know where the tank is on the Contour and under what conditions it is "sweating", but this is what I've noticed on my vehicle.

          I have never observed any "sweating" of the in bed tanks, but they are under a plastic cover which is a pain to remove and would just drip into the bed anyway (as opposed to dripping on the pavement which is very noticeable -- and ALARMING the first time you see it!).

          -- Dan

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          • #6
            Re: Tank sweat..? for Newbies

            Black Mariah, what you describe sounds more like water (condensate) from the exhaust system. Check for holes in the system or leakes around joints. I would consider this, water from the exhaust, system normal. Natural gas will produce more water during the combustion process than gasoline. The exhaust system acts as a condensor until it reaches 212 deg F at the end of the tail pipe.

            Thinking back on this thread, I've never seen a CNG tank cylinder sweat. The only condition that under which I could think of would be during venting of a tank at a rate that would allow the dome of the tank and valve and lines to get cold enough that water from the atmosphere would condense. During defueling (venting) demonstrations, I have vented type 2 cylinders fast enough to have frost forming on the valve.

            Just another view

            Larrycng

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            • #7
              Re: Tank sweat..? for Newbies

              I too in over 20 years, have never seen a CNG tank sweat. I have however, seen a restricted fuel line or a pinched fuel line cause a severe frosting and sweating. I had one case where an improperly cut and deburred fuel line was over 75% blocked and caused a loss of full load power (it would whistle when it was being refilled).

              Franz

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              • #8
                Re: Tank sweat..? for Newbies

                Originally posted by larrycng View Post
                Black Mariah, what you describe sounds more like water (condensate) from the exhaust system. Check for holes in the system or leakes around joints. I would consider this, water from the exhaust, system normal. Natural gas will produce more water during the combustion process than gasoline. The exhaust system acts as a condensor until it reaches 212 deg F at the end of the tail pipe.

                ...
                Larrycng
                Larrycng:
                You are correct sir! I saw the water dripping right after start up today. I looked under the vehicle and saw water dripping from seams in the muffler. It is exactly what you said and has nothing to do with the CNG tank. I looked at that too -- it was clean and dry.

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