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Thread: Fuel Leak in a Tight Spot - Do I Have to Drop the Tank?

  1. #1
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    Fuel Leak in a Tight Spot - Do I Have to Drop the Tank?

    Replaced the in tank fuel pump yesterday.

    Of course, I have a leak from one of the hoses that connects to the fuel pump. Unfortunately the leak is from the rubber hose about 5 inches away from the fuel pump. Apparently when I initially pushed the two fuel hoses out of the way to clear the pump removal and install, this must have stressed the old fuel hose and produced a leak. There is no way to replace that short section of hose from the hole where the fuel pump resides.

    I am thinking the fuel tank will need to be dropped in order to replace this section of hose. I'm going to put the car on the lift tonight and see if there is a way to get to the hose without dropping the tank. Any thoughts on this?

  2. #2
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    Many people take a hole saw to the back seat to gain access to the other end of that hose. Thats what i did.
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
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  3. #3
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    I vaguely remember someone mentioning that and I tried searching, but couldn't find the thread. How big of a hole did you create and where did you drill it? I can peer into the hole where the fuel pump is and can tell there is a hose clamp about 5 inches back that would need to be loosened.
    Last edited by danieldd; 01-30-2013 at 03:36 PM.

  4. #4
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    i drilled a 2 inch diameter hole. there aren't any real measurements. I stuck a measuring tape underneath and measured how far from the fuel tank hole the hose clamp was, then just went for it.


    you may have to cut the hose clamp off..
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  5. #5
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    Quote Originally Posted by legoman67 View Post
    i drilled a 2 inch diameter hole. there aren't any real measurements. I stuck a measuring tape underneath and measured how far from the fuel tank hole the hose clamp was, then just went for it.


    you may have to cut the hose clamp off..
    What did you use to plug the hole back up? I'm thinking a suitable rubber plug maybe?

  6. #6
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    I used a piece of pre-painted sheet metal. You can get something similar at HomeDepot, it can be galvanized too. Cut a circle 3 inches in diameter for a 2" hole and file or sand down the rough edges. Place a bead of silicone around the hole, place the sheet metal disc onto the silicone and weigh it down with a brick or similar until the silicone sets up.
    One word of caution: do NOT use any cutting tools that produce sparks! Place a wet rag over the fuel pump assembly to mitigate any fumes. I used an air nibbler (like tinsnips) to cut the hole in my car. If you ever have to get back under there, a razor blade is all you need to gain access.
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  7. #7
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    You 2 guys have just saved me from dropping the tank!

    Thank you.

    Excellent point about putting a wet rag over the fuel pump. I think I may have access to an air nibbler.

  8. #8
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    i found a grommet at the hardware store that fit the 2" hole perfectly

    and yes, normally im not one to start drilling holes in my car for shortcuts... but dropping the tank is a HUGE PITA. all for one hose clamp.
    Last edited by legoman67; 01-30-2013 at 06:40 PM.
    Current:

    - 09 335i MSport, FBO.
    - 98 Euro M3, Estoril Blue
    - 04 M3, Carbon Black, 6 Speed Coupe
    - 06 M5, Black on Black, Full Leather.
    - 73 3.0CS, Tagia Green, 5 speed M30b35 converted

    Ex's: 1984 325e, 1988 325IX, 1992 525I, 1995 540i/6, 2002 330i, 2005 330xi, 1992 850i, 2003 330i #1, 2003 330i #2, 2002 330ci, 2004 330ci, 2007 328CI, 2007 335i, 2001 M3, 2006 M5 6 speed

  9. #9
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    Agreed. I didn't know how much of an effort it was to drop the tank. The manual simply states to disconnect the various lines, remove the driveshaft, the protective insulation and drop the tank.

    Doesn't sound all that difficult, but then again, I have no direct experience. The more I think about creating a hole for access to the clamp, the more I like it!

  10. #10
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    I was under there changing differentials over the Christmas holiday. Trust me, you don't want to drop the tank if you don't absolutely need to
    Matthew M.
    North Carolina, USA
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  11. #11
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    Quote Originally Posted by danieldd View Post
    Agreed. I didn't know how much of an effort it was to drop the tank. The manual simply states to disconnect the various lines, remove the driveshaft, the protective insulation and drop the tank.

    Doesn't sound all that difficult, but then again, I have no direct experience. The more I think about creating a hole for access to the clamp, the more I like it!
    They "forgot" to mention that you need to drop the complete rear axle carrier assembly, which involves disconnecting the emergency brake cables, brake calipers, etc. It is the grand-daddy of all P.I.T.A. jobs (almost makes you want to part your car out and buy another one).
    General Motors does the same thing with some of their in-tank fuel pumps. They are located on top of the tank with no way to access it without dropping everything back there - all the F-Bodies had this problem.
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  12. #12
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    A pic of where to cut the access hole for reference.
    Attached Images Attached Images

  13. #13
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    Pretty much in the same place I cut as well. I didn't have a 2 inch hole saw. I only had a 1.75, a 2.125, and a 2.5 inch hole saw. I went with the 1.75. I have yet to find a suitable rubber grommet to fit the hole. I may have to use Steffen's advice and just silicone a piece of sheet metal over the hold. BTW - kudos to Steffen for suggesting a wet cloth to cover the fuel pump - to abate any fuel vapors.

    I had my wife hold the shop vac nozzle near the cutting site. Didn't help much as these cutting tools like to project tiny metallic debris throughout the surrounding area. Got it all cleaned up and replaced the fuel hose without incident. Sure beats dropping the tank.


  14. #14
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    Go to home depot or somewhere similar, They have cut outs made up to plug faucet lines and pipe holes, That's what i did.

    ***Change that hose clamp to one without teeth, They seem to not cause hose damage or loosen up on there own***
    Last edited by 8eights; 02-03-2013 at 07:28 PM.

  15. #15
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    Quote Originally Posted by 8eights View Post
    Go to home depot or somewhere similar, They have cut outs made up to plug faucet lines and pipe holes, That's what i did.

    ***Change that hose clamp to one without teeth, They seem to not cause hose damage or loosen up on there own***
    Thanks. I'll check them out.

    With regard to the hose clamp... I reused the original BMW hose clamp on one end of the hose. On the end where it mates up to the fuel pump, I used a new BMW clamp. They are still serrated, but they are convex, so they don't bite into the hose. This is what the BMW tech use in my neck of the woods. I tried to get the ones without the teeth, but they don't carry them.

  16. #16
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    Looking at brand new hole on your pic ... Does not look like it leaked over there ....

  17. #17
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    Quote Originally Posted by perelet View Post
    Looking at brand new hole on your pic ... Does not look like it leaked over there ....

    Picture can be deceiving. It leaked bad. This was the result of bending the hose back on itself whilst removing/replacing fuel pump. Once I replaced the hose, there was no more leak.

  18. #18
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    not enough
    Is this still the only option? This was two years ago so bumping up in case someone came up with an ingenious alternative.

    As I was fiddling with my fuel pump assembly and moving the hoses around I noticed a drip from "back there" in the hoses leading to the carrier. Thinking I have to address this when I actually install the replacement carrier. It just sounds awful to have to cut...but if that's the only way...
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  19. #19
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    It is really not that bad. One you commit to the cut, its done!

  20. #20
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    I wouldn't let that go for too long. this can and will cause irreversible Fire damage to your vehicle.
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  21. #21
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    I recommend checking this for all - as an FYI, one of the our E31 community lost their E31 to a fire from this exact hose (the one coming from the top of the gas tank) within the past 30 days. I am checking mine soon!
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  22. #22
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    Quote Originally Posted by rogbmw View Post
    I recommend checking this for all - as an FYI, one of the our E31 community lost their E31 to a fire from this exact hose (the one coming from the top of the gas tank)...

    ...and it was NOT pretty my friends, and there is absolutely nothing anyone can do except get a safe distance away from the inferno, and hope it is over quick.
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  23. #23
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    Just another maintenance item. There are quite a few hoses back there, and mine are now 21 years old. No leaks so far, but now I am preparing, my wallet for a tank drop, and replacing them all. I have already replaced them from the fuel filters to the engine, to the return hard pipe. Every one was original, a fire waiting to happen. Maintenance is the key to longevity!

  24. #24
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    You don't need to drop the tank (that involves complete rear axle carrier drop with differential, exhaust, and a few other things). The access hole is all you need, since the lines on the top of the tank are actually metal. It is just the rubber lines that are between the fuel pumps and the hard line.
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  25. #25
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    not enough
    i can already see it's going to be difficult using the Oetiker clamps/tool after cutting that hole...unless a bigger hole is cut.

    - - - Updated - - -

    borrowing pic from Wokke so you can see the combination of rubber/metal fuel lines along the tank
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    • File Type: jpg 41.JPG (312.6 KB, 147 views)
    CB42366 - 1991 850i 6-speed. Brilliantrot & Black Nappa Leather
    CD00144 - 1994 850CSi. Hellrot & Black Nappa Leather


    My other projects:
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