X5 4.6is Brakes question and other questions and code info

[BiiQ X5]

Hey, just want information on these things that have popped up lately. I had the car sitting for about 2 years without constantly using it and when I did restart it again I noticed the brake reservoir was empty. Brake pedal went all the way down.

I filled up the reservoir and still the pedal goes all the way down. Now the fluid hasn't drained down and it's been like 4 days since I filled it so if that's the case. What can be the reason for that? My guess is that it has air in the system and I just need to bleed it. Maybe it can be the master cylinder? Need some advice on that.

Also, when I change the auto gear to reverse or drive I feel the whole car like go back and forth, kind of like after you press the brakes and the car wiggles foward and back and feels springy.. not sure of the transmission change can even impact the springs.. can they?

Also the codes that I got with my peake reader

Code E0 msr intervention plausibility??
Code 66 mfl interface??
Code 0f precat o2 sensor slow response (this one is obvious) I will change the sensor.

[andrewwynn]

Fluid didn't evaporate. If the MC reservoir was empty you have a leak somewhere. Add more fluid and pump the brakes the fluid will puddle on the ground.

The most common break is just under the drivers left foot on a left hand drive car. I don't know if they mirror brake lines on RHD cars.

[BiiQ X5]

That's the thing though. It doesn't puddle anywhere. The pedal just goes all the way down. Hasn't lost any fluid.

[andrewwynn]

It lost fluid if you added. There is a lot of plastic that catches fluid.

I think I see what you are saying; pedal went down so you thought low fluid and added. Was the fluid low before you added?

If it got low air could have gotten in and cause pedal to the ground symptom else a possiblity is problem with the master cylinder.

What scanning solution do you have? You need something like foxwell or computer based to bleed abs.

[StephenVA]

My bet is the corroded lines under the driver's side where the master cyl is located. There is a joint in the lines right at the bottom of the firewall that is covered by the big plastic panel under the car. If your lines are split open due to rust and corrosion (In NJ that would be NORMAL), you will need to replace the lines from the joint to the rear wheels. OR add in a 36 inch splice. Lots of posts on this issue. I will find one and bump it so it will be on the slash page.