Control After Start
After engine start, ECM turns ON the coolant pump switchover valve to turn OFF the coolant pump. This stops the coolant circulation.
ECM controls the coolant switchover valve to adjust negative pressure on the vacuum actuator
installed to the coolant pump. Via the vacuum actuator rod, ball rotary valve
is closed allowing the coolant flow to be stopped. This stops coolant to flow to the cylinder head.
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Coolant pump housing |
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Belt pulley |
When all of the following conditions are satisfied, ECM performs the cold start control to deactivate the coolant pump.
- Engine coolant temperature: 85 deg.C (185 deg.F) or less
- Charge air temperature: below threshold limit
- Engine speeds: 4, 000 rpm or less
- No heater request from A/C auto amp.
When coolant pump stop conditions are not satisfied, ECM turns OFF the coolant pump switchover valve. Negative pressure on the coolant pump switchover valve is ventilated through the air vent. The spring force returns the ball rotary valve in the direction flowing coolant. This turns ON the coolant pump, allowing coolant circulation again.