COOLANT SYSTEM
Thermostat Components and Functions
12/05
6LY3 Service Manual
7-17
© 2007 Yanmar Marine International
THERMOSTAT COMPONENTS
AND FUNCTIONS
The thermostat opens and closes a valve according
to changes in the coolant temperature inside the
engine. This controls the volume of coolant flowing
to the heat exchanger from the cylinder head and,
in turn, maintains the coolant temperature in the
engine at a constant level.
The thermostat is a bottom bypass type. It is
located in a position connected with the cylinder
head outlet line at the top of the coolant pump unit.
When the coolant temperature exceeds the
opening temperature, the thermostat opens and a
portion of the coolant is sent to the heat exchanger
and cooled by seawater. The other portion flows
from the bypass line to the coolant pump intake.
The bypass line is closed off as the thermostat
valve opens and is completely closed when the
coolant temperature reaches 81.5°C (179°F). The
valve lifts 4 mm (0.16 in.), sending all of the coolant
to the heat exchanger.
Figure 7-19
Figure 7-19
The thermostat used in this engine is a wax pellet
type, with a solid wax pellet located in a small
chamber.
When the coolant temperature rises, the wax melts
and increases in volume. This expansion and
contraction is used to open and close the valve.
0006217
(1)
(2)
(
3
)
(4)
(5)
(6)
(
8
)
(10)
(12)
(14)
(7)
(9)
(1
3
)
(11)
(15)
No.
Item
Measurement
1
Date of Manufacture
—
2
Jiggle Valve
R21.5 or more
3
Valve Open Temperature
—
4
Adjustment Fittings
Ø8 mm (0.314 in.)
5
Stopper
Ø14 mm (0.551 in.)
6
Piston
Ø6.4 mm (0.251 in.)
7
Pellet
—
8
Valve
t0.8 mm (0.31 in.)
9
Seat
t1 mm (0.39 in.)
10
Attachment Frame
t1 mm (0.39 in.)
11
Spring
Ø3 mm (0.118 in.)
12
Helper Springs
Ø1.8 mm (0.070 in.)
13
Bypass Valve
t0.6 mm (0.023 in.)
14
Pipe
Ø15 mm (0.590 in.)
15
E-Snap Ring
E9
Thermostat Specifications
Opening Temperature
69-73°C (156-163°F)
Full Open Temperature
85°C (185°F)
Valve Lift at Full Open
10 mm (0.393 in.)
