3.0      PROBLEM: Air is not building up more than 6.0 bar while running OR Air drops down to 4.5 bar when vehicle is parked
3.1	Grad. hand brake valve Relay valve - if fitted.	Leak through exhaust.*	Overhaul assembly.*
3.2	System protection valve (SPV)	Leak through SPV element 23 or 24.	Overhaul assy.*
3.3	Spring brake actuators (SBA)	Leak through L - tube indicates main seal / ram defect Leak through SBA service port (with pipelines disconnected and Hand brake released condition) indicates O ring/ram stem defect.	Identify the defective assy and overhaul.
3.4	Hose, pipes & fittings	Leak in 23 and 24 circuit lines.	Check pipe lines & all joints. Rectify/ replace hose assy if damaged
3.5	Ex. brake valve / Lever control valve Foot Control Valve (if engine brake system is fitted)	Leakage through air exhaust or Foot Control Valve.	Overhaul assy.*
3.6	Other aux. assemblies.	Leakage through aux assys, such as air horn, air suspension etc.	Identify defective assemblies and overhaul.