I finally decided to deal with the strong smell of petrol around my car whenever I fill up the tank.
There is a flexible breather pipe which runs from the top of the fuel tank back to near the fuel filler cap, which vents air from the tank when fuel is poured into the tank. This pipe passes through an aperture in the car and it rubs against an edge on the fuel tank side of this aperture, eventually causing a small hole in the pipe and allowing excess fuel to dribble whenever the fuel level is high.
I took some photos to help with reassembly, but thought I would post them on this forum with some notes in case it is of help to anyone. I have included details of fastener types and torques wherever possible.
Before starting, it makes the job a lot easier if the fuel tank is almost empty. Otherwise, drain as much fuel as possible from the tank into a suitable container.
Slightly loosen the nuts on the rear right-hand side wheel, since the hand brake and propeller-shaft will already be disconnected when it is time to remove the wheel.
2. Remove centre console:
Remove the gear knob by pulling firmly upwards (do NOT twist). On the M-Sport, the gear knob is glued to the gaiter, so it is best to grip around the top of leather gaiter. The frame of the gaiter is held in by four plastic lugs. Carefully detach the gaiter from the centre console trim.
The centre console trim panel is secured by eight metal spring clips. Use a pry tool to remove the panel, taking care to protect the surface of the plastic console.
Remove the two plastic covers and remove the screws underneath (10mm hex socket).
Move both front seats forward to provide better access to the rear section of the centre console. Use a pry tool to release the top edge. Release clips either side near the carpet by carefully reaching underneath or use a suitable pry tool. Disconnect the cable connected to the air-vent and remove the rear section of the centre console.
Remove the two screws (10mm hex socket). Unplug the two connectors indicated and snip the cable tie. (I have also inserted an M5 washer on either side of the arm rest hinge to cure a rattle.)
Move the seats back to a mid-way position. Open the storage compartment and carefully pry the handbrake gaiter out of the centre console.
The centre console can not be removed because it fouls on the hand brake. To overcome this problem, release the handbrake, then reach beside the handbrake press upwards on the black plastic lever below the handbrake mechanism whilst simultaneously lifting the hand brake lever. The hand brake lever should now lift much higher than normal (about 6 notches further than normal). This allows the centre console to fit over the handbrake so it can be removed upwards and towards the rear.
3. Disconnect airbag control unit:
First disconnect the battery negative terminal (12mm hex socket, 5Nm) then wait a few moments to be sure that there is no power on the airbag system.
Remove the foam cover from the airbag control unit. Unplug the two connectors indicated, by opening the plastic levers. Then remove the two nuts and one bolt (10mm hex socket, 8Nm). Note the position of the negative lead and ensure it is replaced during reassembly.
Remove the airbag control unit, taking care to avoid static discharge.
4. Disconnect handbrake:
Use a medium (approx 6.5mm) flat screwdriver to push the handbrake adjusting spring backwards and engage the locking mechanism.
Lift the plastic cable tray out of its two rear mounting points, to access the handbrake balance arm. Open the black plastic retaining clips on the balance arm, then lever the handbrake cable anchors out of the balance arm.
Finally, use the screwdriver to release the handbrake adjusting spring, back to its normal position.
5. Remove rear seat:
Whilst working inside the car, it is a good time to remove the base of the rear seat. Firmly lift the front edge of the seat to unclip it on the left and right. Feed the seat-belt buckles through the openings in the seat. Then remove the seat.
6. Remove exhaust:
Raise and secure the back of the car, then support the rear of the exhaust system.
Release the eight M8 bolts securing the under-body reinforcement plate (T50 Torx bit, 30Nm).
Unfasten the four nuts between the downpipes and the exhaust (15mm hex socket, 45Nm). If these nuts are corroded then they will be difficult to release. Replace the four M10 copper nuts during reassembly (P/N 18301737774).
If necessary, soak the nuts/bolts overnight in penetrating oil (PlusGas). Any broken bolts can be drilled out and replaced, but it is time consuming and best avoided.
Tap the joint with a mallet to free the exhaust from the downpipe.
Details of the exhaust system will vary for different models, but these images are for the standard exhaust on an E90 330i.
Unfasten the exhaust clamp (E10 Torx socket, 21Nm).
Unfasten the front hanger (18mm hex socket, 30Nm).
Unfasten the left rear hanger (E18 Torx socket, 21Nm).
Unfasten the right rear hanger (E10 Torx socket, 21Nm).
Disconnect the hose to the pneumatic valve which activates the exhaust flap.
With help from a second person, remove the temporary exhaust support and lower the exhaust away from the car.
Upon reassembly, either replace the two gaskets (P/N 18107549447) or apply copper grease to the mating faces.
7. Remove under-body panels:
Remove the front and rear sections of the heat shield, then the triangular and mid sections of the plastic under-body panels.
Remove the left and right under-body covers adjacent to the rear wheel arches. Each cover is secured by two plastic screws (T30 Torx bit) and two small plastic expanding rivets. The rivets can be removed using a pry tool and pliers, or alternatively the centre pin can be punched out. The rivets will probably need to be replaced (P/N 51161881149).
I also removed the long left and right side under-body panels, but this may not be absolutely necessary.
8. Remove propeller shaft:
Mark the position of the propeller shaft relative to its connections, so that it can be reassembled in the same relative position.
Raise at least one of the rear wheels off the ground so the propeller shaft is free to rotate. Put the transmission in first gear to lock the propeller shaft. Start removing the three M10 bolts connecting the rear giubo to the differential input (E12 Torx socket, 20Nm + 90º). It will be necessary to put the transmission in neutral and rotate the propeller shaft to gain access to all bolts.
Put the transmission in neutral so the propeller shaft is free to rotate. Remove the three M12 bolts connecting the front giubo to the output of the transmission (18mm hex socket, 55Nm + 90º). Use an 18mm open-ended spanner to hold the nut while turning the bolt. The spanner fits through the transmission mount, which also provides a convenient anchor point for the spanner.
Remove the two bolts securing the propeller shaft centre joint (13mm hex socket, 21Nm) and lower the centre mount so that the propeller shaft is in a ‘V’. First detach the rear of the propeller shaft from the differential input flange then detach the front of the propeller shaft from the transmission output flange.
Upon reassembly, clean and apply suitable grease to the centre mounts at each end of the propeller shaft. BMW recommend Dow Corning Molykote Longterm 2 Plus. Important: Upon reassembly replace the three nuts and six bolts (P/N 26117526140, 26117523709, 26127536563) and ensure that they are correctly torqued.
9. Remove handbrake guide tube:
Remove the six bolts securing the handbrake guide tube (10mm hex socket, 8Nm). Pull the guide tube towards the rear and feed the handbrake cables out of the car.
The rubber gasket should be replaced (P/N 34406764925) if it is damaged.
10. Remove wheel arch cover:
Remove the right rear wheel. Release six screws (8mm hex socket) and five plastic nuts (10mm hex socket). Free the outer edge of the wheel arch cover from around the wheel arch where it meets the car body. Then feed the cover downwards and out of the wheel arch.
11. Remove fuel tank:
There are two circular metal covers located under the black insulating material which lies beneath the rear seat. Remove the four screws from each of these covers (10mm hex socket) and lift up the covers. Disconnect electrical plugs. Under the left cover, disconnect the fuel feed line by pressing the grey ring away from the fuel line. Under the right cover, disconnect the fuel vent line by pressing the quick-release fastener.
Inside the wheel arch, disconnect the fuel breather pipe from the top of the fuel filler pipe by pressing the quick-release fastener. It might help to also twist the breather pipe to help work it free.
Unfasten the hose clamp (6mm hex socket, 4Nm) on the fuel supply hose at the rear of the fuel tank. Place a suitable container under the tank then disconnect the hose. There may be a dribble of fuel depending on the residual level in the tank. There is a non-return flap at the mouth of the opening. Insert a clean screwdriver or similar implement into the opening to release the non-return flap and allow any remaining fuel to drain into the container.
Support the fuel tank as there will probably still be some fuel remaining in it.
Remove the bolt securing the centre of the tank (13mm hex socket, 19Nm). Remove the two bolts securing the retaining straps on the left and right sides of the fuel tank (13mm hex socket, 19Nm). Remove the two retaining straps and the two exhaust heat shield retaining brackets.
Lower the fuel tank from the car. Empty any remaining fuel from the tank as it will be easier to refit when it is empty.
Detach the old breather hose by pressing the quick-release fastener and replace with a new vent pipe (P/N 16126765748) and a protective tube (P/N 16124390434). The old damaged breather pipe looked like this.
This is the aperture that the pipe rubs against.
The new breather pipe looked like this, although the first image does not show the protective tube, since I opted to slide it through from the wheel arch.
Reassemble the components following the reverse process.
Pour at least 10 litres of fresh fuel into the tank. Check operation of the hand brake, although it should not be necessary to adjust the hand brake.
This job took two days, including taking photographs and cleaning many of the components removed from the car.