COOLING SYSTEM CAP [SKYACTIV-G 2.0]

Purpose, Function

• The cooling system cap keeps the engine coolant passage at a higher pressure than the barometric pressure when the engine coolant is at a high temperature, and prevents air bubbles from forming in the engine coolant by increasing the engine coolant boiling point.

  In addition, the cooling system cap maintains appropriate pressure in the engine coolant passage and prevents system damage and hose detachment by changing pressure in the engine coolant passage.

Construction

• The cooling system cap is located on the water outlet.

  

• The cooling system cap consists of parts shown in the figure.

  

Operation

1. The engine coolant expands and the pressure in the engine coolant passage increases when the engine coolant is at a high temperature. At this time, the pressure valve closes by the spring force of the cooling system cap pressure valve which increases the pressure in the engine coolant passage and increases the engine coolant boiling point.

2. When the engine coolant temperature increases further and the pressure in the engine coolant passage exceeds the spring force of the pressure valve, the pressure valve opens and the engine coolant in the engine coolant passage flows out to the coolant reserve tank.

3. The engine coolant flows out and the pressure in the engine coolant passage decreases, and the pressure valve closes when the spring force of the pressure valve and pressure in the engine coolant passage are nearly equal.

4. Vacuum is generated in the engine coolant passage when the engine coolant temperature decreases and the engine coolant contracts. The vacuum valve opens if the vacuum is more than the spring force of the vacuum valve and the engine coolant in the coolant reserve tank returns to the engine coolant passage.

5. The pressure in the engine coolant passage is appropriately maintained and malfunctions are prevented by performing steps 2) through 4) according to the engine coolant temperature (pressure in engine coolant passage).