[iscab]

The dealer told me not to use the high pressure washes because they may cause leaking.

I think it is totally dependent of the position of the car relative to the spray and pressure of each wash.

I have felt a little water on one wash out of about 15. So I don't worry too much about it.

But once water is coming through, you are in a bad position in the wash - you are getting too much pressure on a vulnerable area around the window. So if you feel any water, you should immediately move the car a few inches. I always keep a couple of micro-fiber towels in my car...anything can happen while driving with the top down or in a high pressure wash. I would really like to get out of the habit of a high pressure wash, but a quick basic wash for $5 is very tempting. The thing is it doesn't really do a great job anyway. It gets the rough stuff usually, but not film on the paint. I have even seen times it does not get all the bird crap off. Maybe yours is even higher pressure than the one I use.

Remember every time you open the door on these cars, the windows come down 1/2" and the windows roll back up when you close the door - so there is a margin for error there, as small as it may be. But pressurized water will eventually find it!

I hate to say it but unless there is a problem with your seals or windows, this is a "normal" issue. Disclaimer, I have a 2011 335is, not a 2008 335i.