This is usually located in the engine bay on the other side of the dividing bulkhead to the brake pedal
Examine for leaks and/or corroded pipes leading to the unit.
Rubber pipes should not be split or show damage or wear.
The fluid in the reservoir should be in between the min and max levels as indicated on the side of the reservoir.
Make sure the top cap is in place to prevent fluid spillage.
Check around the cylinder for any signs of leakage.
Brake fluid levels
Brake Fluid Specifications