I have a Cat TH83 S/N-3RN01562. Both the parking brake and service brakes are not working. The guy who ran the machine never told me and he no longer works for me so don't really know when or why they stopped working. Fluid reservoir is full. When you press brake pedal with engine off it goes to the floor. With engine running there's a slight kick back but still goes to the floor.
See the attached. It explains the fundamentals regarding how the brake system works and how to troubleshoot/adjust it.
Thank you sir!!