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Thread: Fuel leak at wing root need help!

  1. #1

    Fuel leak at wing root need help!

    Hello, my name is Jack I have a 1978 C23 Sundowner that I love. Unfortunately I have developed a fuel leak on the lower side of the left wing root; there is no visible dripping just small amount of the blue die appearing out towards the leading edge. We removed the interior trim and the access plate of the fuel sending unit and see no signs of the gasket leaking or any fuel stains. I know there is a threaded plug up towards the leading edge that I guess could be leaking but we see no way of accessing it because it is on the other side of the front wing spar. My mechanic wanted me to check message boards to see if anyone has any advice. He either wants to take the wing off or punch a hole in the fuselage. I would think if there is a leak at the seam it could be sealed by removing the sending unit and accessing the inside that way. Any help or suggestions wouldbe greatly appreciated as am literally sick over the problem.
    Last edited by Jklosterman; 11-24-2016 at 11:55 AM.

  2. #2
    Welcome to BAC !!!

    I say, try to seal it from the inside.

    Here is a pic of the inside of the tank looking forward from the fuel sending unit hole. That is the forward spar carry through bolting to the heavy Beechcraft inboard tank extrusion.

    Here are two pix of the inboard / fuselage side of the wing.
    Attached Images Attached Images

  3. #3
    Thank you for the pictures, Is this leak a common problem?Is it most likely the seam or do you think it could be the bolt plug depictedtowards the front of your picture. Is there any access to that bolt/plug?

  4. #4
    It will be very difficult to seal this from the inside. That forward spar will be an issue, as it blocks or limits access forward of it. This would be a great time to introduce an eight to eleven year old kid to the joys of aircraft maintenance.

    I'm a pro seal B 1/2, guy. But this would probably be a better job for B 2 hour sealant, as it is thinner and messier.

    Look at those sealed seams between the skin and the extrusion. I'm guessing that is your problem area. Pro Seal B 2, an acid brush and a kid just might fix this one.

    Look at the small hole at the corners of the spar carry through. That might give you a shot up those seams with a small brush. Beech did a very nice pretty job in here. You should not worry about that. Be wild, crazy and generous with that sealant.
    Last edited by wdnd5960; 11-24-2016 at 01:58 PM.

  5. #5
    Thanks again for taking the time to respond on Thanksgiving Day.This leak is all I can think about. So if I understand you correctly the best approach in your opinion is to try and apply sealant by gaining access to the inside of the tank thru the sending unit opening.

  6. #6
    Quote Originally Posted by Jklosterman View Post
    Thank you for the pictures, Is this leak a common problem?Is it most likely the seam or do you think it could be the bolt plug depictedtowards the front of your picture. Is there any access to that bolt/plug?
    My guess is a skin seam. But hit everything while your in there.

    The only access to the bolt plug is through that hole in the spar hole. My forearm will not make the turn in this tank compartment to get there. Maybe a kid or small lady could do it. But sealing from the inside will have many times the success rate of trying to seal it from the outside.

    The shop manual calls for Pro Seal B 1/2 sealant to be used. Read the tank reseal procedure in the shop manual at chapter 3-10C & 10D. If you do not have a shop manual, I think you can find it in the download section of this wonderful website.

    Happy Thanksgiving!

  7. #7
    Quote Originally Posted by Jklosterman View Post
    Thanks again for taking the time to respond on Thanksgiving Day.This leak is all I can think about. So if I understand you correctly the best approach in your opinion is to try and apply sealant by gaining access to the inside of the tank thru the sending unit opening.
    Your welcome!

    There are a lot of people that support you on this site full time!

    This is your best bet for success.
    Last edited by wdnd5960; 11-24-2016 at 01:59 PM.

  8. #8
    The MM Section 3-10 covers resealing the tank in place (not removing the wing). First you identify the leak by slightly pressurizing the tank and doing the soapy water/bubble search. Sealing thru the fuel sender is fairly straight forward from the inside, the inaccessible areas the procedure requires drilling #40 holes thru the skin but not the rib at .45 inch intervals and squirting sealer in one hole til it comes out the other. I've never done that and it sounds iffy to me. I have however seen inspection plates installed in the inaccessible areas and proseal applied from the inside.

    To answer your question: No, this is not very common. The tanks appear to stay sealed unless there is some stress on the wing.

    Rap

    Rap McBurney
    N28848

  9. #9
    Check the sender gasket first. A leak from here can travel down and give the appearance of a leak in another location. It is behind the panel inside the cabin.

  10. #10
    Sorry didn't read where you already checked this out

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