BMW E38 brake calipers and brake pedal
Why is the E38 brake pedal soft or does it go far down after changing the brake pads?
The cause can be a wrongly installed rear caliper spring that pushes the pads away from the disc, or worn grooved discs that the new pads do not seat against. A rusty piston surface can also prevent the pad from seating. New pads need a little driving before they feel normal.
Is it normal for the brake pedal to be hard before starting the engine?
Yes. The brake booster works only when the engine is running, so the pedal softens after starting. If the pedal softens too much, check the booster vacuum hose: it may be loose at the intake manifold connector or dried out.
How do you keep the brake calipers working so they do not seize?
Clean and lubricate the slide pins and free up the pistons once a year. Brake fluid should be changed every couple of years. Thick paint behind the pads can also prevent them from moving in the caliper bracket.
Why do the rear brakes stay stuck on even though the pads and calipers are fine?
The cause can be a master cylinder that does not release pressure from the rear brakes; in that case the master cylinder is replaced. In winter the pedal can freeze if there is water in the brake booster, and then the booster is replaced.