Yanmar 3YM30, Service Manual

Page: 187 / 231

9. Cooling water system
166
9.5 Pressure cap and coolant recovery tank
9.5.1 Pressure cap construction
The pressure cap mounted on the filler neck
incorporates a pressure control valve. The cap is
mounted on the filler neck cam by placing it on the
rocking tab and rotating. The top seal of the cap seals
the top of the filler neck, and the pressure valve seals
the lock seat.
9.5.2 Pressure cap pressure control
The pressure valve and the vacuum valve seal both the
valve seats, when the pressure in the fresh water
system is within the specified value of 88 kPa (0.9 kgf/
cm
2
). This seals the fresh water system.
When the pressure within the fresh water system
exceeds the specified value, the pressure valve opens,
and steam is discharged through the overflow pipe.
When the fresh water is cooled and the pressure within
the fresh water system drops below the normal value,
atmospheric pressure opens the vacuum valve, and air
is drawn in through the overflow pipe.
The coolant recovery tank (which sill be described
later), keeps the water level from dropping due to
discharge of steam when the pressure valve opens.
9.5.3 Pressure cap inspection
Refer to 2.2.6(4).
Action of pressure control valve
Pressure valve
Open at 82-109 kPa
(0.84-1.11 kgf/cm
2
, 0.82-1.09 bar)
Vacuum valve
Open at 8 kPa
(0.08 kgf/cm
2
) or below
Pressure cap
Pressure valve
spring
Copper tube
Filler neck
Overflow pipe
Fresh water cooler