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Thread: DIY: 2001 740i fuel tank replacement (implosion issue)

  1. #1
    Join Date
    Jan 2008
    Location
    Plano, TX
    Posts
    81
    My Cars
    2001 E38 M Sport

    DIY: 2001 740i fuel tank replacement (implosion issue)

    Within 1 year of ownership, the fuel tank fell a victim to the infamous fuel tank implosion issue. It started leaking really bad and needed to be replaced. In addition, I had to replace the charcoal evaporative return module located in the rear fender on the driver side (US) as it was throwing codes. I disconnected negative battery cable for the job.

    1. Put the car on jack stands, remove rear wheels. This is what my tank looked like on the bottom, it was soaked with gas to the point that I could not leave the car in the garage as the smell of gas propagated into the house through the vents and the furnace blower.



    2. One of the hardest bits for me was the exhaust disconnection from the CATs. The bolts seized and even did not look like bolts at all. I had to take the car to a shop where they carefully torched them out for me. Most shops did not want to do it due to the gas leak in the rear. The hazard freaked them out and I could understand them. This is what my disfigured factory bolts looked like:



    3. If you are lucky and your bolts are in good shape, the above step should be a breeze as these bolts are easily accessible. Now, the rest of the exhaust system needs to be unbolted. It is pretty easy in the M62 E38. First thing to do is to support the exhaust system from falling. I used one hydraulic floor jack on casters. It makes it very easy to roll the entire exhaust system from under the car by just pulling it from the back once the bolts/nuts are removed. Hydraulic floor jacks are also very useful during the final alignment of the new gas tank and removal of the old tank by supporting both sides from underneath. At some point, it will make the job a lot easier if you are able to lower the tank on each side independently and move it to each side a bit in order to undo breather lines which are located on both sides of the tank. If you have two floor jacks, it is a piece of cake. I can imagine that things can be more cumbersome if you can't independently support each side of the tank. My suggestion is to have two floor jacks around.

    Before removing the bolts and nuts, disconnect the oxygen sensors. I did not picture this step, but it is very straight forward. Once the exhaust is supported in the way pictured below, remove the bolts from the center bracket first (these are also not pictured, sorry.)



    ...then remove these bolts in the back on each side



    ...and finally, these rear muffler brackets at the very back on each side



    4. Now you can lower the supporting floor jack just a bit and pull on the exhaust from the back. It is easy to balance and rolls out easy.



    ...I parked it in the driveway for the next day under an old car cover




    5. Remove heat shield. I forgot to take pictures of it. It is held by several screws that are easy to find and take minutes to take out.

    6. Disconnect e-brake cable at the rear. Did not need any tools for it. There is a manual clip and it separates easily. Move the e-brake cable out of the way so it is not in the way of the fuel tank.

    7. Disconnect the drive shaft from the differential. Mark its position first so it is reconnected in the same way. This may not be necessary, but I did it anyway. Move the drive shaft to the side like in the pic below so it is not in the way. It stayed in this position until the very end. Make sure you have some grease ready for the re-assembly:



    8. Another thing I forgot to take a picture of are the bolts that hold the tank in place. Fortunately, they are very easy to see from the bottom. There are total 4 of them. First two are the large brackets that run underneath the tank on each side and only have a bolt at one end of the bracket. After you remove the brackets, place the jack stands under the tank so it does not hang on the breather lines. Remove the other two bolts.

    9. Disconnect the fuel lines and filler hose on the right side. There are two connections for the fuel lines on the front of the fuel tank and one filler hose on the back. I purchased a new filler hose to go with the new tank and threw the old one away without detaching it from the old tank.

    10. The breather lines are on the top of the tank and are difficult to reach unless you lower the tank a little and move it to the side in order to expose them. Here is the view of the breather hoses on the driver side (US) after the tank was lowered by a few inches and moved to the right by a few inches. They are right in front of the VDO level sensor seen on the picture. There is also one connection on the right side where the fuel pump is (not pictured). Disconnect it as well:



    11. After the lines are disconnected, lower the tank down and out. Here is the view with the tank removed. The arrows show breather line connections on both sides. Three connections total:



    12. Roll the new tank in and lift it up almost all the way to reconnect these lines. Here is the view of the new tank going in on two floor jacks:



    13. Reconnect breather lines, fuel lines, and filler hose. This would be a good time to replace the fuel filter since there is no gas in the system and it will spare you the spills.

    14. Reconnect the hand brake cable and drive shaft.
    15. Reinstall the exhaust in reverse order.

  2. #2
    Join Date
    Feb 2015
    Location
    Phoenix, AZ
    Posts
    840
    My Cars
    1997 740iL (5/96 build)
    great job, great post. well done.
    1997 740iL; 5/96 build. Purchased 12/04. Off the road build project 2013 - 2021. back on road 3/2021. Became daily driver (only vehicle) 6/12/2021. Still not completed. Stay tuned as the adventure continues.

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