Porter-Cable JOB BOSS C3550 - Manual (Page 24)

24- ENG A08193
PROBLEM CAUSE
CORRECTION
Knocking Noise. Possible defect in safety
valve.
Operate safety valve manually
by pulling on ring. If valve still
leaks, it should be replaced.
Compressor mounting
screws loose. Tighten mounting screws,see
Parts manual for torque
specifications.
Carbon build-up in pump. Have checked by a Trained
Service Technician.
Squealing
sound.
Compressor pump has no
oil. See Oil-Checking paragraph in
the Maintenance section.
Defective check valve. Remove and clean, or replace.