Thermostat Components And Functions - Yanmar 6LY3 series Service Manual

Thermostat Components and Functions

12/05
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
(1) (2)
(4)
(5)
(6)
(7)
(8)
(9)
(10)
(11)
(12)
(13)
(14)
(15)
Figure 7-19
6LY3 Service Manual
(3)
0006217
© 2007 Yanmar Marine International
No. Item
1 Date of Manufacture
2 Jiggle Valve
3 Valve Open Temperature
4 Adjustment Fittings
5 Stopper
6 Piston
7 Pellet
8 Valve
9 Seat
10 Attachment Frame
11 Spring
12 Helper Springs
13 Bypass Valve
14 Pipe
15 E-Snap Ring
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.
Thermostat Specifications
Opening Temperature
Full Open Temperature
Valve Lift at Full Open
COOLANT SYSTEM
Measurement
—
R21.5 or more
—
Ø8 mm (0.314 in.)
Ø14 mm (0.551 in.)
Ø6.4 mm (0.251 in.)
—
t0.8 mm (0.31 in.)
t1 mm (0.39 in.)
t1 mm (0.39 in.)
Ø3 mm (0.118 in.)
Ø1.8 mm (0.070 in.)
t0.6 mm (0.023 in.)
Ø15 mm (0.590 in.)
E9
69-73°C (156-163°F)
85°C (185°F)
10 mm (0.393 in.)
7-17