I thought that when your pedal goes halfway down then is hard as a rock (not spongee), with little effect and that pumping makes it seem like you have zero brakes and can't push it to the floor that it's a blown booster? But I'm not sure...
:dunno:

Brake pedal should firm up and not move farther that is normal it should never continue to go down so exciting what you mean

So I have more info, as I've been busy and haven't had time to mess with the X5. If I hop in and press the brake pedal it feels like a normal pedal. If I hold it down and start the pedal sinks and then feels like it hits a hard stop like the master cylinder is bottoming out. I get the feeling that the brake booster is working as if it was failed there would be no difference. If I keep the pedal down to where it feels like it is bottomed out, and turn of the engine there is no difference in pedal feel. If I let up, and press the pedal it feels normal. One of these mornings when it is cool, I will get it up off the ground and get the wheels off to inspect the brake lines. If I don't see anything at that point, I will dig into it further. I've also just watched this video, and since I was parked nose down at a steep grade for several days I'm betting oil fouled the pump so I'm going to order the gasket kit and do that as well.

https://www.youtube.com/watch?v=9nRroLFTPJc

https://www.youtube.com/watch?v=QogQ8Ip04Vk&t=2s -Brake booster test.

If you start the engine and pump the brakes and then hold the brake and it goes to the floor there is a leak and it should show as loss of fluid in the brake fluid reservoir if not externally visible. Master cylinder failure symptoms are the similar.

Brake line leaks are usually major leaks while a leak at the calipers are more often the small leaks. Check

The condition of the brake fluid in the reservoir should be be translucent regardless of the color of the fluid when it was new. Contaminated fluid is usually brown and opaque. If this happened all of a sudden it would not contaminated fluid.


Do you have brakes at all. Can you run it up to 60 mph and stop in a reasonable distance?

No way am I taking it up to 60 MPH. If I'm going 30 and stab the brake pedal it slows down pretty quick. the last bit to a complete stop is the hardest part. I have the vacuum seal kit on its way and I will dig into it a bit this weekend.

I also need to have the valve seals done. Do you have a shop in DFW that you trust? I don't want to pull the heads.

Have done my own work for so long any recommendation would be extremely out of date. Only time I have used a shop is when I had Dinan stuff installed in 2002. At that time you had to have it installed at an authorized Dinan shop. I used Classic BMW for that.