TM  10-3930-643-34 BRAKE  TROUBLESHOOTING  AND  MAINTENANCE. 8-1. Service  Brake  Troubleshooting. MALFUNCTION TEST  OR  INSPECTION CORRECTIVE  ACTION d. LOW AIR PRESSURE. Step 1. Check air compressor belt. Adjust or replace if necessary, refer to paragraph 8-14. If belt is good, go to Step 2. Step 2. Inspect governor. Repair or replace governor, refer to paragraph 8-15. If governor is good, go to step 3. Step 3. Inspect air compressor discharge valves to determine if valves are leaking. If valves are faulty, repair or replace, refer to paragraph 8-14. If valves are good, go to Step 4. Step 4. Inspect for a restriction in discharge line or in discharge cavity of air compressor. Remove and clean cylinder head, refer to paragraph 8-14. If no restriction is found, go to Step 5. Step 5. Inspect for restriction in inlet valves. Remove cylinder head and clean inlet valves, guides, springs and inlet ports, refer to paragraph 8-14. If no restriction is found, go to Step 6. Step 6. Inspect air compressor inlet valves for faulty operation or worn parts. Repair or replace inlet valve if necessary, refer to paragraph 8-14. If valve is good, go to Step 7. 8-3