A leak of brake fluid could lead to a change in brake pedal feel and overtime a degradation in braking performance increasing the risk of a crash.

Brake fluid containing polymers is used that acts as lubricants for certain brake system components. If replacement brake fluid is used that does not contain such polymers, or that contains only small amounts, a part of the rubber seal located at the rear of the brake master cylinder may become dry, and the seal may curl during movement of the piston.

What to do: Book this in with a dealer now. It affects a safety system.