The pipe that goes in to the brake caliper feels brittle and shows signs of cracking.
There appear to be fluid patches underneath the car when it's been parked up for a while.
The brake pedal has lost the resistance it used to have and now travels all the way to the floor without much effort.
It feels like you have to press the brakes all the way in to make the car stop, they 'bite' at a much lower point than they used to and it sometimes feels like the car won't stop.