GUIDE:
1. Fully turn the steering to the right to give access behind the driver's front wheel to work. [Removing the wheel will give more access but is not necessary.]
2. Remove the 6 screws holding securing the rear half of the felt wheel-arch liner in place using an 8mm socket. This will allow access without removing the arch-liner completely. Four of the screws are located in the wheel well itself and two are located underneath next to the sill.
3. Remove the plastic 'mud-guard' trim on the outside of the wheel-arch that adjoins the felt arch-liner. This is done by pressing the centre-pin of the 3 plastic clips through the clip and then removing the clips with a panel-popper tool. [It may be possible to do the job without removing this trim piece, as the clips are very hard to get out and prone to breaking, but visibility and access are certainly improved].
4. Peel the felt wheel-arch liner out from the rear lip of the wheel-arch and if possible tuck it behind the wheel. The washer-bottle should now be visible to the rear of the front wheel. It sits in a tight gap between the outer and inner wings of the car body itself and access is very limited. [This is unlike E39, E60 etc. where the bottle sits left-to-right across the rear of the wheel-arch and access if much easier!]
5. Remove the windscreen washer hose from where it enters the pump and move it out of the way.
6. Slide a long flat-screwdriver in between the washer-bottle and the outer wing and prize the pump upwards until the spout is clear of the bottle and the pump can wedged up and out of the way.
7. The clogged filter should now be sitting in the washer-bottle where the spout of the pump fits. Use the flat-screwdriver to prize the filter up and out of the bottle. It should now be removable by hand or using long-nose pliers / tweezers.
8. Clean the gauze filter using water and lightly brush it with a sponge-scourer or stiff brush. [I find an old toothbrush works perfectly.] It is likely clogged with a 'gel' like substance that builds up supposedly due to the use of incorrect washer-fluid as well as dirt from the bottom of the tank if the washer has been run without fluid in for a while, but should clean up pretty easily.
9. Carefully slot the filter back into the washer-bottle and press it back into place using long-nose pliers / flat screwdriver or both, making sure it is fully seated.
10. Slide the pump spout back into the filter / washer-bottle, making sure it is fully seated and rotated to the correct position with the spout for the windscreen-hose pointing to the side of the car.
11. Refit the washer-hose, trim, wheel-arch liner and wheel. [Reverse steps 1-5.]
www.e90post.com/forums/showthread.php?t=930107
http://www.bimmerfest.com/forums/showthread.php?t=737416
http://forum.bmw5.co.uk/topic/120732-f10-windscreen-washer-not-working/
http://forum.bmw5.co.uk/topic/124943-f10-washer-problems/