Subaru IMPREZA GD 2007 Series Manual page 76

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B: INSPECTION
1. RELATIONSHIP OF ENGINE COOLANT
CONCENTRATION AND FREEZING
TEMPERATURE
The concentration and safe operating temperature
of engine coolant is shown in the diagram. Measur-
ing the temperature and specific gravity of the cool-
ant will provide this information.
[Example]
If the coolant temperature is 25°C (77°F) and its
specific gravity is 1.054, the concentration is 35%
(point A), the safe operating temperature is –14°C
(7°F) (point B), and the freezing temperature is –
20°C (–4°F) (point C).
• Diagram 1
Safe operating temperature
1.100
1.090
1.080
1.070
B
C
1.060
(1.054)
1.050
1.040
Freezing
1.030
temperature
1.020
1.010
1.000
-40 -20 -10
-30
(-40) (-22) (-4) (14) (32) (50) (68) (86)
Coolant temperature
Engine Coolant
Concentration
of coolant
60%
50%
40%
A
30%
20%
10%
0 10 20 30 40
(104)
C ( F)
CO-02172
CO(H4SO)-17
2. PROCEDURE TO ADJUST THE
CONCENTRATION OF THE COOLANT
To adjust the concentration of coolant according to
temperature, find the proper engine coolant con-
centration in the diagram 1 and replace the neces-
sary amount of coolant with an undiluted solution of
engine coolant (concentration 50%).
The amount of engine coolant that should be re-
placed can be determined using the diagram 2.
[Example]
Assume that the engine coolant concentration must
be increased from 25% to 40%. Find point A, where
the 25% line of engine coolant concentration inter-
sects with the 40% curve of the necessary engine
coolant concentration, and read the scale on the
vertical axis of the graph at height A. The quantity
of coolant to be drained is 2.1 2 (2.2 US qt, 1.8 Imp
qt). Drain 2.1 2 (2.2 US qt, 1.8 Imp qt) of coolant
from the cooling system and add 2.1 2 (2.2 US qt,
1.8 Imp qt) undiluted coolant solution.
If a coolant concentration of 50% is needed, drain
all the coolant and refill with the undiluted solution
only.
• Diagram 2
Necessary Concentration
of coolant
3
(3.2,
2.6)
A
2
35%
(2.1,
30%
1.8)
25%
1
20%
(1.1,
0.9)
10% 15%
0
10 20
Concentration of coolant in
the vehicie cooling system %
Concentration of coolant in vehicie
and quantity to be drained
COOLING
45%
40%
30 40 50
CO-00012