Losing Brake Fluid - 2004 X5, 3i
 

I changed brake pads, rotors and calipers on all 4 wheels, bleeded the system starting from the furthest to the master cylinder, RR, to the closest, FL. Ever since then, I keep losing fluid a lot in spite of having a pretty good braking performance and hard brake pedal. The fluid in the reservoir keeps going down to the minimum level. No apparent leakage on the road. Once I fill the reservoir, it only takes a couple of miles or so before the red alarm comes on indicating low level of brake fluid. And starts again. I must have done this at least 3 or 4 times so far. Where the hell does the fluid go. Leakage in the booster would show inside the car on the driver side, but it's dry.

Any guidance would be much appreciated.

I would check bleed screws and brake hoses at each caliper because you just did it.

But the most common brake fluid leak is under the car, below the driver's seat behind the plastic cladding.. Remove a couple of rivets and screws to flex the cladding to get a look with a flashlight.

Also, your X5 is not a manual trans car is it? If it is, you could be losing brake fluid thru the clutch hydraulics.

Any brake fluid in the vacuum hose coming off your brake booster?
Potential bad seal in the master cylinder with brake fluid getting sucked into the engine.

That fast of leak almost certainly in the rear line under the left front seat. There is a design defect that causes this failure.

Mine blew out dramatically from a deer related fast stop. The panel well hold a lot of fluid before it drips out but usually it will puddle by the time the low fluid light comes on. I think your leak is slow enough your are just leaving drips along the way

look for fluid residue on the inside of your rims. I had this happen one time when I didn't tighten up a bleed valve sufficiently (always scared of stripping those things due to an incident years ago).

You are in Ontario Canada, so likely salt corrosion of the metal lines that run along the left side underchassis.

I wrote a DIY in this forum...

If it wasn't leaking prior to your work and the engine is running the same then check your work very carefully first.

Second the leaking brake line under left seat area where line turns 45 degrees and subject to rust, mine leaked and had spongy pedal but able to stop due to safety system with essentially 2 separate cross systems, get it fixed soon.