Don't open the headlights -- try methanol first. It's very easy and safe to do and the headlights can be removed in only a few minutes. I posted this DIY a little while back with before and after pics.

https://5series.net/forums/e60-discu...lights-137264/

 

Someone know if it is possible to clean the xenon-lens without opening the headlight?
Seems like the lens is getting some milky white fog, that is taking some of the light.

On a E90 I can get the lens out without opening the headlight, but not on my own car

Anyone done this?

 

i will try menthanol. yup i read your your DIY . i have no choice, i will not take the risk to open my headlights...
thanks all ,

 

But what`s the best way to clean the outside of the headlights?

 

I think the best way is restoring protection coating by 2K urethane clear coat. I sanded headlights (sandpaper from 180 to 5000), then I used a primer for polycarbonate and finally sprayed by 2K clear coat. See pics, before and after: