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Thread: Fuel Leak - Cheap, quick, Easy Fix

  1. #1
    Join Date
    Dec 2008
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    Richmond, Va
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    BMW E36 318i

    Fuel Leak - Cheap, quick, Easy Fix

    Before you start working on this, UNPLUG your negative side of the battery.

    Go to a boat store and buy a small container of MARINE-TEX putty. It cost me $16 at Boaters World. Get the WHITE colored putty. This stuff is great for patching gas tanks. I found out about this stuff when I used to own a boat and had a leak in my 64 gallon tank.

    After experiencing this common problem recently with the fuel leak and what I did to fix it, I want to let other BMW 318i E36 DIY'rs know what I did to fix it.

    I started experiencing the strong fuel smell, especially after filling up the tank. The smell was so strong, I stopped parking the car in the garage any more for fear of explosion and blowing up my house.

    OK. Let me just get to the fix and save yall the long story and the big $$$ that dealers want to charge to render this problem.

    1) Remove the rear back seat. Just pull up on it on both corners, the yank it out of there.

    2. Now you can see the two round impressions in the plastic, insulation covering that is under your seat. There are two, one behind the passenger seat and one behind the driver's seat. These are the plates that cover the fuel sending unit and the fuel pump.

    3. Lift up to expose the access plates, unscrew the plates to get access. In my case, the leak was behind the driver's seat. Unplug the electrical connector to the fuel pump, so it will be out of your way. This is the top of the fuel pump. There was alot of dirt and debri from trees that some how got in there. All soaked with gasoline. Tip- use an air compressor or compressed air and blow what debri you cant get up with a rag out of there so that the white plastic plate is very clean.

    Now you will see what is causing the problem. It may be hard to see it, but in my case, there was a hair line crack in the seams of this plastic covering.

    Mix up your Marine-TEX as per directions. Now dab a good amount over the hair line crack that the gas is seeping out from. When this stuff hardens, the seems will now be better than new.

    Your done! (Well... after you put everything back together.)

  2. #2
    Join Date
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    I have also used this in the past. Figured it was worth a shot. Worked well!

  3. #3
    Join Date
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    Yep. worked great. Before I found out where it was leaking from, I took the car to a shop and they wanted to charge me $350 to take the gas tank out so they could find the leak. I declined to let them do the work. When I got home, I did some more digging and realized there was a second access hatch under the back seat that I had not checked out. The one that was leaking was behind the drivers seat.

  4. #4
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    Hmm. Very interesting, I'm going to have to check that out. I get the smell of fuel from around my left rear wheel after filling all the way up.
    "Fist in the air and a finger to the sky.
    Do I care if you hate me?
    Do you wanna know the truth?
    C'est la vie,
    Adiós,
    Good riddance,
    F--- you.

    I'm under and over it all."

  5. #5
    Join Date
    Dec 2008
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    Yep, it saved me $400! The shop wanted to charge me $350 to pull the tank off the car. Then would have probably wanted to replace the fuel pump.

    Also, make sure that the screw ring is tight. just grab it and see if you can turn/tighten it by hand. Mine was loose.

    This is an easy one. just pull out your back seat, lift up the fiber covering the round plates. 4 small phillips head screws hold the plate down. Then you will see the white plate with 2 fuel lines going in to the fuel sending unit. You will need a rag to clean that top with. Its going to be a hair line fracture somewhere in that cap. If you dont see anything, dont be discouraged. check the plate on the other side, behind the drivers seat. I had all kinds of crud sitting on top of the plastic caps that was soaking in gas.

    Good luck!

  6. #6
    Join Date
    Sep 2008
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    Hayward, CA
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    97 z3 1.9M, 96 328ia
    Quote Originally Posted by carl6405 View Post
    Yep, it saved me $400! The shop wanted to charge me $350 to pull the tank off the car. Then would have probably wanted to replace the fuel pump.

    Also, make sure that the screw ring is tight. just grab it and see if you can turn/tighten it by hand. Mine was loose.

    This is an easy one. just pull out your back seat, lift up the fiber covering the round plates. 4 small phillips head screws hold the plate down. Then you will see the white plate with 2 fuel lines going in to the fuel sending unit. You will need a rag to clean that top with. Its going to be a hair line fracture somewhere in that cap. If you dont see anything, dont be discouraged. check the plate on the other side, behind the drivers seat. I had all kinds of crud sitting on top of the plastic caps that was soaking in gas.

    Good luck!
    did you mean the drivers side of the rear seats?

  7. #7
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    Quote Originally Posted by carl6405 View Post
    Yep, it saved me $400! The shop wanted to charge me $350 to pull the tank off the car. Then would have probably wanted to replace the fuel pump.

    Also, make sure that the screw ring is tight. just grab it and see if you can turn/tighten it by hand. Mine was loose.

    This is an easy one. just pull out your back seat, lift up the fiber covering the round plates. 4 small phillips head screws hold the plate down. Then you will see the white plate with 2 fuel lines going in to the fuel sending unit. You will need a rag to clean that top with. Its going to be a hair line fracture somewhere in that cap. If you dont see anything, dont be discouraged. check the plate on the other side, behind the drivers seat. I had all kinds of crud sitting on top of the plastic caps that was soaking in gas.

    Good luck!
    Hey, I saw some stuff in the auto paint section at WalMart that's for underwater repairs. I don't remember the name but it comes in a tube and you're supposed to cut a chunk off, knead it until warm, and then put it on. Think this will work the same? It's about $5 for the tube.
    "Fist in the air and a finger to the sky.
    Do I care if you hate me?
    Do you wanna know the truth?
    C'est la vie,
    Adiós,
    Good riddance,
    F--- you.

    I'm under and over it all."

  8. #8
    Join Date
    Dec 2005
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    Philippines
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    bmw e36 M3
    maybe i'll give this a shot to save some money. when i checked mine the hose is corroded.(behind the passenger seat) it's like the clamp destroyed the end and an inch of the hose. so when i put it back its like leaking at the end of the hose? or do i just have to look for a fracture or a cut on the hose. in addition, i guess i have to check the driver side too. a mechanic told me that we have to put down the gas tank and when i heard that i know it will be expensive.

  9. #9
    Join Date
    Dec 2008
    Location
    Richmond, Va
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    BMW E36 318i
    Go with Marine - TEX. When it comes to gas under pressure, better go with what works and you dont want to have to do it twice.

  10. #10
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    That other stuff was Permatex. I got some JB Weld that says it's for plastic gas tanks.
    "Fist in the air and a finger to the sky.
    Do I care if you hate me?
    Do you wanna know the truth?
    C'est la vie,
    Adiós,
    Good riddance,
    F--- you.

    I'm under and over it all."

  11. #11
    Join Date
    Oct 2006
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    Duarte, land of rocks
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    588
    My Cars
    1993 325is
    Clean it up with carb cleaner, follow it up with simple green.
    I would scuff it up with sand paper so the epoxy can get a good grip. Maybe leave the gas cap lose while it cures. I need to check my car it smells like gas around it too.
    It's a no smoking zone.!

    KP

    PS, I just finished repairing the tank in my Skipjack (welded no glue).

  12. #12
    Join Date
    Oct 2015
    Location
    Orlando
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    BMW E90 (2008 328i)
    Quote Originally Posted by carl6405 View Post
    Before you start working on this, UNPLUG your negative side of the battery.

    Go to a boat store and buy a small container of MARINE-TEX putty. It cost me $16 at Boaters World. Get the WHITE colored putty. This stuff is great for patching gas tanks. I found out about this stuff when I used to own a boat and had a leak in my 64 gallon tank.

    After experiencing this common problem recently with the fuel leak and what I did to fix it, I want to let other BMW 318i E36 DIY'rs know what I did to fix it.

    I started experiencing the strong fuel smell, especially after filling up the tank. The smell was so strong, I stopped parking the car in the garage any more for fear of explosion and blowing up my house.

    OK. Let me just get to the fix and save yall the long story and the big $$$ that dealers want to charge to render this problem.

    1) Remove the rear back seat. Just pull up on it on both corners, the yank it out of there.

    2. Now you can see the two round impressions in the plastic, insulation covering that is under your seat. There are two, one behind the passenger seat and one behind the driver's seat. These are the plates that cover the fuel sending unit and the fuel pump.

    3. Lift up to expose the access plates, unscrew the plates to get access. In my case, the leak was behind the driver's seat. Unplug the electrical connector to the fuel pump, so it will be out of your way. This is the top of the fuel pump. There was alot of dirt and debri from trees that some how got in there. All soaked with gasoline. Tip- use an air compressor or compressed air and blow what debri you cant get up with a rag out of there so that the white plastic plate is very clean.

    Now you will see what is causing the problem. It may be hard to see it, but in my case, there was a hair line crack in the seams of this plastic covering.

    Mix up your Marine-TEX as per directions. Now dab a good amount over the hair line crack that the gas is seeping out from. When this stuff hardens, the seems will now be better than new.

    Your done! (Well... after you put everything back together.)
    I love this idea. I went and bought the product to fix the hairline crack in the top of the unit, but my problem is, when i wipe it clean, fuel seeps right back out of the crack. Is there a way to relieve the pressure so it stops? Because the fuel comes back out, it doesn't allow the marine tex to fully adhere, and the leak continues. I have disconnected the battery, took off the gas cap, but it doesn't help. I see the black hose connected but 1. i can't see how to detach it, 2. if i detach it will it be able to go back. and 3. will detaching even help?

    I know this is an old post, but any help would be awesome. I have a 08 328i sedan.

  13. #13
    Join Date
    Jan 2015
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    Fort Myers, FL
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    E92 335i
    Quote Originally Posted by Tpayankee View Post
    I love this idea. I went and bought the product to fix the hairline crack in the top of the unit, but my problem is, when i wipe it clean, fuel seeps right back out of the crack. Is there a way to relieve the pressure so it stops? Because the fuel comes back out, it doesn't allow the marine tex to fully adhere, and the leak continues. I have disconnected the battery, took off the gas cap, but it doesn't help. I see the black hose connected but 1. i can't see how to detach it, 2. if i detach it will it be able to go back. and 3. will detaching even help?

    I know this is an old post, but any help would be awesome. I have a 08 328i sedan.
    I have this same exact issue on my fuel filter that's hairline cracked.. I can wipe it clean and the gas seeps back out.. I tried everything you did and it still does it, not sure how to get that gas to stop seeping.. Did you find a way..?

  14. #14
    Join Date
    Oct 2012
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    Detroit, MI
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    1,976
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    E36, E70, i3
    Just replace it. Can be done in 10 minutes.

    What the heck.

  15. #15
    Join Date
    Jun 2010
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    NY
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    1997 328i
    Fuel filter? it's like $10!

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