Obvious Signs of Failure:
* Brake pedal going all the way to the floor: This is the most obvious sign. If you have to pump the brake pedal repeatedly to get any braking force, or if the pedal sinks slowly to the floor when held, the master cylinder is likely failing. This indicates a loss of hydraulic pressure.
* Spongy or soft brake pedal: A less extreme version of the above; the pedal feels soft and gives more than it should before engaging the brakes.
* Brake fluid leak: Look for brake fluid leaks around the master cylinder itself. This is a clear indication of a seal failure within the cylinder. You might see fluid dripping or staining on the master cylinder or nearby components.
* Unusual brake noises: While not always indicative of master cylinder failure, squealing, grinding, or other unusual noises from the braking system can sometimes accompany a failing master cylinder, particularly if the leak is causing parts to rub.
* Brake warning light illuminated: This light might come on because of low brake fluid level resulting from a leak. While not always a master cylinder problem, it warrants immediate investigation.
Less Obvious Signs (Require More Investigation):
* Gradual reduction in braking effectiveness: If your brakes seem less effective over time, it could indicate gradual internal wear and leakage within the master cylinder.
* Pulling to one side during braking: While usually attributed to issues with calipers or wheel cylinders, a failing master cylinder *can* contribute to uneven braking if it's failing in only one circuit.
Important Note: If you suspect a problem with your master cylinder, do not drive the vehicle. A failing master cylinder drastically reduces your braking ability, making driving extremely dangerous. Have it inspected and repaired by a qualified mechanic as soon as possible. Ignoring these symptoms can lead to brake failure and accidents.
