Today I decided that with all this talk of failing roof motors, plus the so called summer coming to an end, that checking the roof motor drain would be a good idea. A couple of notes and observations after following shipkillers document:
1) If you don't have some axle stands, don't do this job! Your head, and chest possibly, will be under the car :!:
2) Safety goggles are useful too. The amount of crap that drops down is quite a lot!
The bung is not where I expected it to be, it's quite close to the bodywork of the car. I'd expected to find it behind the access hatch.
Anyway, a few pics you might find useful: (from the phone, so apologies for quality)
You don't need the wheel off, although if you have large hands, you might want to. I didn't but will next time. You will need it jacked up though to have enough room to get a socket on the bolts. A spanner is just too fiddly.
To remove the access cover you undo these three first. The outer two are 8mm, the middle one is 10mm. Just to make life interesting
Then there is a fourth 8mm under the car that is not shown in Shipkillers pdf. It's right inside close to the sill
It'll then lift out. If you need any force at all, something isn't right. It sits in a recess in the splash guard mount.
You don't actually need to remove the splashguard. According to Shipkiller's guide there should be two expanding rivots, mine had one and an 8mm bolt. Either there are differences by year of mines been done before and the broken rivot replaced by an 8mm bolt. As the other side had two rivots I'm guessing mine has been done before so
to the previous owner.
There is also a nut similar to the centre one on the access panel in the wheelarch. That's a PITA to get at and almost impossible to see. You'll want a torch and a long extension for your socket. You don't need to remove this one, the splashguard is slotted so loosening it is enough. I couldn't get a decent pic of this.
Here's the rivot I removed. Do be careful, they are easily broken. I had a trim remover tool and this works perfectly. Again, little to no force required :!:
By removing this and loosening the 8mm and hard to reach 10mm you can push the splashguard back towards the centre of the car and then get under and you'll see the bung which just pulls out. If you do decide to remove it, take heed of shipkillers warning about the ABS sensor wire. On mine it is tie-wrapped to the splashguard and if you are ham fisted you will probably do something expensive :!:
The whole thing is a bloody stupid design and I was tempted to leave the bung out as it's well protected and was actually quite clean. There was a little crud in the bung, but otherwise OK. The crud that was in there would have fallen through if no bung had been in place! I ran some water through from the top and all came out OK and cleanish.
HTH
8)
The other guy said afterwards that he was driving it as hard as he could and that he might have been able to creep by on the straights if they had been longer, but couldn't match me in the corners. He was a bit miffed that £10K of mods still only brought his M3 up to Z4M spec 
Well, needed my 'fix' after being deprived for 2 weeks 
