Flight Crew Instrument; Flight Crew Private
Flight Crew Last 90 Days 6; Flight Crew Total 1425; Flight Crew Type 425
Situational Awareness
Aircraft Equipment Problem Less Severe; Ground Excursion Runway
Flight Crew Overcame Equipment Problem; General Maintenance Action
Aircraft
Flew to ZZZ1 on a personal pleasure flight with normal/uneventful landing. Departed ZZZ1 for ZZZ. Upon contacting ZZZ tower was directed to enter left base RWY 25. Flew uneventful visual approach and touched down just passed the numbers at approximately 75-80 knots. Upon applying brakes left brake pedal reacted normally while right pedal appeared to depress to the stop with no/minimal back-pressure or braking apparent on right wheel. Continued to apply maximum possible left pedal/brake pressure while modulating nose wheel to the right in order to continue braking while staying on the RWY and began pumping right pedal/brake. Near end of RWY right pedal/brake began to respond to pumping and right brake effectiveness sufficiently to bring the aircraft to a full approximately 20 feet into the gravel over-run area at the departure end of the RWY. Right brake pedal then gave solid pressure and normal braking and the aircraft was taxied back to the pavement and then clear of the RWY via the taxiway. Further testing while stopped showed both right and left brakes to be functioning properly therefore Ground control was called with request to taxi to hangers which was executed carefully and with normal brake function.As a note; toe brakes and parking brake system were used during taxi and runup operations at both ZZZ and ZZZ1 prior to outbound and return flight as well as landing at ZZZ1 and gave no indication of malfunction at those times.Subsequent inspection revealed debris in the right brake master cylinder and the piston O-ring to have become fairly hard with a slight indentation along approximately 5 degrees of the circumference of the O-ring. Cause of the malfunction is believed to be a result of aged o-rings with subsequent reduced elasticity exacerbated by debris which may have wedged between the o-ring and cylinder wall reducing the ability of the right master brake cylinder to build sufficient braking pressure. Braking effectiveness returned upon pumping of the brake pedal apparently dislodging the debris and allowing the o-ring to have sufficient contact with the cylinder wall. It is surmised that debris may have entered the system via the fluid filler hole during level checking at a recent annual inspection. Logbooks show previous master cylinder rebuild or o-ring replacement to be more than 10 years ago.CORRECTIVE ACTIONS:Both brake master cylinders were rebuilt using new o-rings obtained from Cessna parts. Area around filler holes was cleaned of debris; hydraulic fluid and debris flushed from system; and system was reassembled and proper operation verified.Further; a brake check line item has been added to the landing checklist to be performed after gear down to determine brake function prior to landing. Check consists of depressing the brake pedals and observing proper pedal height and resistance.
The pilot of a Cessna 210 reported that during rollout the left brake pedal felt normal and the right brake went all the to the stop and had no braking effect of the right main gear wheel; resulting in a runway excursion.