The vent hole in the brake master cylinder reservoir tank cap is too small, and therefore a negative pressure is created inside the tank at a cold ambient temperature. In such a condition, a braking action can cause a small amount of air to penetrate into the brake cylinder through the cylinder seal. If this problem is left unattended, it may result in a spongy feeling brake pedal and cause abnormal noise, and in the worst case, the brake warning light is illuminated and the play of the brake pedal increases.
