Air Compressor - Continued

compressor is mounted to the left side of the engine. An unloader

valve in the cylinder head vents compressed air when pressure exceeds

the predetermined level.

On some compressor models, the lubricating oil is carried from the

engine main oil gallery to the compressor by a flexible line. Oil

leaking past the compressor bearings drains into the compressor

mounting base. A return line connected to the mounting base returns

the oil to the engine crankcase.

On other compressor models, lubricating oil is carried to and from

the air compressor through passages in the compressor mounting base.

The compressor mounting base oil passages align with oil passages in

the engine crankcase and the compressor.

The compression of air in the compressor creates so much heat that

the compressor must be cooled. Some compressors are air cooled while

others are water cooled from the engine's cooling system. Aircooled

compressors have cooling fins around the cylinders and the cylinder

head. Watercooled compressors have water jackets either in the

cylinder head or around the cylinders. A water inlet line and a

water outlet line connect the compressor water jacket to the engine

The compressor has aircheck valves, one intake and one exhaust valve

for each cylinder. The valves are held closed by light spring

tension. In each cylinder the intake valve is opened by the suction

created by the cylinder piston on its downward (intake) stroke. The

exhaust valve is opened by air, compressed in the cylinder on the

piston's upward (exhaust) stroke. An air strainer is mounted over

the air compressor air intake port. The air strainer inlet is

connected to the engine air intake system.

During the intake stroke of either compressor cylinder, air is drawn

through the air strainer and intake valve and into the cylinder. On

the exhaust stroke, the air compressed in the cylinder holds the

intake valve tightly closed and opens the exhaust valve. The

compressed air then flows through the exhaust valve into the

compressed air system through an air discharge line connected to the

compressor.

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