Looking for a little insight here. I just got a new to me 2004 530i and I was driving yesterday and the pedal went to the floor and I got a low brake fluid warning.
I assumed that the previous owner just never kept up on it and the fluid got low and some air got into the system. I proceeded to just do a full brake fluid flush and topped everything off.
It was fine for about another hour's worth of driving, until I got the low fluid warning again. Now I remember that the rear's were difficult to bleed, and that got me to thinking that there must be a bad leak somewhere else. I pulled off the plastic underbelly pan, and low and behold there was about a 1/2 gallon of brake fluid sitting in there. I had my wife pump the brakes for me a few times and I found a pinhole leak in one of the coated steel hard lines that run from the firewall to the back under the driver's seat. There were two lines and the one that failed was the outer most line closest to the driver's door. There was areas of corrosion all over it actually.
So my question is, is this common? And do I need to order a new line form the dealer? Or is it better to just fabricate one? I saw that it connected to another line towards the rear, but I wasn't able to see up into the firewall where it connects to in the front. Is this a DIY project? Anyone have any experience with this?