Troubleshooting issues with your brake master cylinder requires some basic knowledge of car mechanics. You may never have changed or checked this part before and if you are new to the mechanical side of motoring, you will require some good suggestions on what to listen and look for. Here are some ways you can use to diagnose the more common problems associated with this part.
INSPECT THE BRAKE PRESSURE
One of the major signs that your brake master cylinder is failing will be a lack of brake pressure when you depress the brake pedal. If you sit with your foot on the pedal and press it a few times, then keeps it be right to the floor, it will make you know how soft it actually is. Very soft brake pedal movement is as a result of a brake master cylinder failure. It is not completely possible to fully repair a master cylinder so you will need to have it changed.
CHECK BRAKE FLUID LEVELS
Low brake fluid levels in the master cylinder will create braking problems and a soft feeling in the brake pedal when depressed. If you there are no signs that the fluid levels are low or leaking then you can look to the failure of the master cylinder as the main reason of this issue. Make sure the fluids are safe in the reservoirs and closed correctly and that the lids are firmly in place.
CHECK THE METAL BRAKE LINES
The metal brake lines that lead to the brake master cylinder can be rusty and develop a leak. Fluid can also leak via the O-rings inside the cylinder. If this is the issue, you will not see particularly visible signs of brake fluid escaping, but if you use a clean rag and run it along the brake lines you will be able to see if any wet fluid is escaping. If there are no signs, then again, it points to problems with the brake master cylinder.
INSPECT THE MASTER CYLINDER GROMMETS
There is a plastic reservoir linked to the master cylinder that keeps the brake fluid. That reservoir is planted on to the metal part of the master cylinder by rubber grommets. These will allow for some level of regular movement caused by the brake pedal and pressures of the fluids. However, they can weaken, break down, and then leak fluid. You will be able to see visible brake fluid leaking from this case.
If you have completely checked all the exterior components and have found no symptoms of anything that points away toward problems with other parts, then you can safely conclude that the brake master cylinder is failing or has already failed. Putting all the above situations to the test will allow you to take out other possible causes of any symptoms which show sign of the same behavior as a faulty brake master cylinder.