The **spongy feel** when pressing the brake pedal is due to the **presence of air in the braking system**. This occurs because the braking system uses a special fluid, called **brake fluid**, to transmit force from the pedal to the wheels. This fluid must be free of air to function properly.

- **Brake fluid**: It is crucial that the brake fluid reservoir is filled to the appropriate levels and that the fluid is in good condition. If there is air in the system, the fluid cannot transmit force efficiently, causing that spongy feel.

- **Operation of the braking system**: When you press the pedal, the brake fluid transmits the force to the pads or shoes, which are responsible for stopping the wheels. If there is air in the system, this force transmission is affected, causing a spongy feel.

- **Solutions to brake problems**: Although overheating of the pads or lack of brake fluid can cause other problems, they are not responsible for the spongy feel. Air in the system is the only factor that causes this specific symptom.

Therefore, it is important to ensure that the braking system is well maintained and free of air to avoid this sensation and ensure effective braking.