Impreza F4-2.5L (2008)
Coolant: Testing and Inspection
INSPECTION
RELATIONSHIP OF ENGINE COOLANT CONCENTRATION AND FREEZING TEMPERATURE
The concentration and safe operating temperature of engine coolant is shown in the diagram 1. Measuring the temperature and specific gravity of the
coolant will provide this information.
[Example]
If the coolant temperature is 25 degrees C (77 degrees F) and its specific gravity is 1.054, the concentration is 35% (point A), the safe operating
temperature is -14 degrees C (7 degrees F) (point B), and the freezing temperature is -20 degrees C (-4 degrees F) (point C).
PROCEDURE TO ADJUST THE CONCENTRATION OF THE COOLANT
To adjust the concentration of coolant according to temperature, find the proper engine coolant concentration in the diagram 1 and replace the necessary
amount of coolant with an undiluted solution of engine coolant (concentration 50%).
The amount of engine coolant that should be replaced 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
intersects 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 l (2.2 US qt, 1.8 Imp qt). Drain 2.1 l (2.2 US qt, 1.8 Imp qt) of coolant from the cooling system and add 2.1 l (2.2 US qt,
1.8 Imp qt) undiluted engine coolant solution.
If a coolant concentration of 50% is needed, drain all the coolant and refill with the undiluted solution only.