BMW M4 Brake pedal is spongy Inspection at your home or office.

Common reasons for this to happen:

• Air in the Lines: If air gets into the brake lines, either due to low brake fluid in the master cylinder or from other source, it will create a spongy feel and reduce your stopping ability. This is sometimes a common occurrence after an inexpert brake pad replacement or repair. Air should be bled from the system after every repair to ensure proper operation and safety.

• Damaged Caliper: Another potential problem that could cause a spongy brake pedal is a damaged brake caliper. If the caliper’s piston seal has started to leak, this will create a soft pedal. Brake fluid may also contaminate the surface of the rotor and/or brake pads, leading to further problems.

• Master Cylinder Wear: If your master cylinder is older, it can sustain enough wear and tear that it loses fluid pressure. This is generally caused by a fluid leak at the master cylinder. Again, any loss of fluid pressure will lead to a brake pedal that feels spongy or soft.

• Brake Line Damage: Your vehicle has both rubber and metal brake lines, and either type can be damaged. When this happens, the line may become crimped, which reduces the flow of fluid through it, or it may begin leaking, which will reduce overall pressure. Both conditions lead to a spongy or soft brake pedal.

• Moisture in Brake Fluid: If your brake fluid hasn’t been changed in a while, there’s a good chance that it has absorbed moisture. Moisture can be absorbed through the pores on rubber brake lines, leading to a spongy or soft brake pedal.