Gather all your tools and materials. Install the fender covers to protect the paint finish. Clean any dirt or grime off the master cylinder reservoir cap with the shop towels. Use brake fluid test ...

Check the brake fluid and the master cylinder reservoir cap gasket. The fluid should be a clear yellowish to light brown. If ...

but like brake calipers, sometimes it can spring leaks or otherwise fail, and it must be rebuilt or replaced. The master cylinder is topped by the brake-fluid reservoir, which must be kept full.