# SDR COZA20161217101

- Type: Service difficulty report (as reported; unverified)
- Difficulty date: December 15, 2016
- Submitted: December 18, 2016
- Operation: Air carrier
- Aircraft: [N733KA](https://openairdocs.org/aircraft/N733KA), registered now
- Make and model: Boeing 737-86N
- Registry model: [Boeing 737-86N](https://openairdocs.org/model/boeing-737-86n) (OpenAirDocs)
- Aircraft serial: 28643
- Aircraft time: 43,801 hours, 23,436 cycles
- System (JASC): [3610 · Pneumatic Distribution System](https://openairdocs.org/jasc/3610)
- Part: Valve
- Part number: 32144464
- Part serial: 5625
- Condition: Sticking
- Location: Zone 500
- Stage of operation: IN
- How discovered: O
- Nature of condition: O
- Precautionary procedure: K
- FAA source: FAA Service Difficulty Reporting System (https://sdrs.faa.gov/)
- Page: https://openairdocs.org/sdr/COZA20161217101

## Discrepancy

DURING MAINTENANCE ENGINE RUNS, NOTED LEFT ENGINE BLEED PRESSURE WAS LOWER THAN THE RIGHT ENGINE AT IDLE POWER SETTINGS.  THE LEFT ENGINE BLEED AIR PRESSURE WOULD RISE AND MATCH THE RIGHT PRESSURE ONCE THE POWER LEVERS WERE ADVANCED TO CHANGE THE ENGINE BLEED SOURCE FROM HIGH TO LOW STAGE.  USING THE FIM AND A DESCRIPTION OF THE SYSTEM OPERATION, DETERMINED EITHER THE HIGH STAGE REGULATOR OR HIGH STAGE VALVE TO BE AT FAULT.  REPLACED THE LEFT HIGH STAGE VALVE.  PERFORMED AN ENGINE RUN AND THE LEFT AND RIGHT ENGINE BLEED PRESSURES MATCHED AT IDLE POWER SETTINGS CORRECTING THE PROBLEM.

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