Symptoms of a bad master cylinder include leaking fluid, fading pedal and bad brake fluid. When the brake pedal starts to sink, becomes unresponsive or feels spongy, the master cylinder is malfunctioning. A bad master cylinder does not transfer the power from the brake pedal to stop the vehicle safely.
Symptoms of a bad master cylinder include external and internal leaks. When brake fluid is leaking from the seals, the driver should notice a leak at the back of the master cylinder bore. In some cases, a leak near the vacuum booster or inside the vehicle shows signs of a bad master cylinder.
When a vehicle is turned off, the brake pedal should remain firm. However, if the driver pushes the pedal lightly and it sinks to the floor, the master cylinder has an internal leak. If the brake pedal is fully depressed and feels unresponsive or spongy, this is the result of a malfunctioning master cylinder.
Another symptom of a bad master cylinder is bad or contaminated brake fluid. Noticing brake fluid in the reservoir that contains water or dark-colored fluid displays a problem with the master cylinder. This type of contaminated brake fluid can cause rubber seals in the cylinder to deteriorate, which leads to the leak. Stuck ABS valves and calipers are another symptom of a bad master cylinder.