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Introduction 

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WABCO

 Maintenance Manual 31 (Revised 08-18)

Operation

The compressor is driven by the engine and its crankshaft turns 
continuously while the engine is running. Compression of air is 
controlled by the 

governor

 and by the 

compressor’s unloading 

mechanism

.

The 

governor

 maintains the brake system air pressure at preset 

maximum and minimum levels. The governor is mounted apart from 
the compressor, either horizontally or vertically. The governor port is 
located on the crankcase of the compressor. Figure 1.3.

Figure 1.3

The 

unloader mechanism

 controls the air compression cycle; an 

air compression cycle has three phases:

1.

Induction:

 Air flows from the engine to the compressor, 

opening an inlet valve in the cylinder head of the compressor.

2.

Compression:

 Air pressure is increased, causing the 

compressor’s discharge valve to open.

3.

Unloading:

 Air passes from the cylinder to the inlet chamber of 

the cylinder head via a port controlled by a sliding leaf valve.

When system cut-in pressure is reached, air is exhausted from 
the unloader port.

4.

After unloading, the unloader piston returns the sliding leaf 
valve to the loaded position. This seals the unloader ports and 
compression resumes. Figure 1.4.

Figure 1.4

Maintenance Intervals

The WABCO System Saver 318 air compressor receives inlet air, oil 
and coolant from the engine, so it is important to follow the engine 
manufacturer’s recommendations and maintenance schedules 
regarding fluid levels, air filter and recommended change intervals.

Cylinder Head

Remove carbon deposits from the discharge cavity and rust and 
scale from the cooling passages of the cylinder head.

Clean carbon and dirt from the inlet and unloader passages.

NOTE: 

Shop air may be used to blow the carbon and dirt deposits 

from the unloader passages.

Figure 1.3

GOVERNOR
PORT

1003374b

Figure 1.4

1003375b

SLIDING LEAF

VALVE

Summary of Contents for System Saver 318

Page 1: ...NON THROUGH DRIVE THROUGH DRIVE SYSTEM SAVER 318 AIR COMPRESSOR FOR MACK E TECH AND ASET ENGINES MAINTENANCE MANUAL...

Page 2: ...Follow your company s maintenance and service installation and diagnostics guidelines 4 Use special tools when required to help avoid serious personal injury and damage to components Hazard Alert Mes...

Page 3: ...2 Operation Maintenance Intervals Cylinder Head 3 Visual Inspection 4 Section 2 Troubleshooting 7 Section 3 Compressor Replacement Compressor Replacement Information Removal 8 Installation Cylinder He...

Page 4: ...Notes...

Page 5: ...ing above 250 psi in the event of a blocked discharge line or other malfunction Figure 1 1 Description The WABCO System Saver 318 air compressor provides and maintains air under pressure to operate de...

Page 6: ...valve to open 3 Unloading Air passes from the cylinder to the inlet chamber of the cylinder head via a port controlled by a sliding leaf valve When system cut in pressure is reached air is exhausted f...

Page 7: ...maintenance program Figure 1 5 Figure 1 5 Figure 1 5 1003376b Check air inlet and discharge ports between compressor and governor Check under plate or at power steering pump for leakage Check water p...

Page 8: ...urer s oil and filter maintenance schedules are followed Restricted air inlet or excessive vacuum present at compressor inlet Verify engine or compressor air cleaner is functioning correctly Replace i...

Page 9: ...Refer to air dryer manufacturer s service instructions Chafed or worn discharge line Replace faulty sections of discharge line Loose or leaking air line connections Verify all connections are secure T...

Page 10: ...orn or damaged unloader piston O ring porosity in unloader piston bore loose or leaking seal at unloader piston bore Replace compressor cylinder head assembly Compressor head gasket failure Discharge...

Page 11: ...The front of the WABCO System Saver 318 air compressor is mounted to the engine Before you remove the compressor make sure you have a replacement gasket to install with the new compressor Mack part nu...

Page 12: ...al to verify that the installation is to the correct specifications 8 Add engine coolant to the cooling system Use the coolant recommended by the engine manufacturer Visually inspect the engine and co...

Page 13: ...leaf The two holes in the sliding leaf must be installed over the two pins on the base of the cylinder head Figure 3 6 Figure 3 6 3 Position the inlet valve on the bottom of the cylinder head Align t...

Page 14: ...sor does not reach governor cutout pressure check for air leaks in the system If reservoir volume and engine RPM are per original vehicle manufacturer s specifications system plumbing leakage must be...

Page 15: ...in 40 countries For more information visit www wabco na com NYSE WBC is a leading global supplier of technol ogies and services that improve the safety efficiency and con nectivity of commercial vehi...

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