Variable Coolant Pump

Courtesy of JAGUAR LAND ROVER NORTH AMERICA, LLC

The variable coolant pump is located at the front of the cylinder block. A pulley is attached to the pump flange.

The pulley is driven by the accessory drive belt at engine speed. For additional information, refer to: ACCESSORY DRIVE

The variable coolant pump is controlled to give the minimum flow to support all cooling requests from the engine components. The variable coolant pump has a shroud inside that slides over the impeller to prevent engine coolant from being pumped into the engine. The variable coolant pump generates internal pressure, used to move the shroud.

Pressure is generated with every rotation of the variable coolant pump. This pressure is then diverted either to the shroud assembly or leaked back to the engine cooling system, which is controlled by a solenoid valve. Therefore, the shroud will not move if there is no rotation of the variable coolant pump.

The shroud solenoid is controlled with a Pulse Width Modulation (PWM) signal from the Powertrain Control Module (PCM). For additional information, refer to: ELECTRONIC ENGINE CONTROLS

Any request from 0 - 100% flow can be fulfilled at most engine speeds, contributing to the whole engine thermal management strategy. The internal pressure within the variable coolant pump acts against a return spring in the housing. Without a signal from the PCM  the solenoid is open. Therefore the shroud returns to its base position under spring force, resulting in full flow from the variable coolant pump.

During engine cold start, the impeller is fully covered by the shroud, therefore no engine coolant is pumping into the cylinder block. As components warm up, the flow request will increase in five stages. The variable coolant pump is controlled to give the minimum flow to support all cooling requests from the engine components. Upon engine coolant temperature reaching 85°C (185°F), the shroud will move to its furthest position. This allows maximum pumping, with temperature control managed by the PCM  and the electric thermostat.

The flow modes of the variable coolant pump are the following:

• 0 = Zero flow
• 1 = 12% flow
• 2 = 25% flow
• 3 = 50% flow
• 4 = Full flow (default position).

The PCM receives input signals from the following components to calculate the level of cooling required:

• Cylinder head temperature sensor
• Cylinder block temperature sensor
• EGR  temperature sensor
• Ambient Air Temperature (AAT) sensor
• Engine coolant temperature sensor
• The Terrain Response switchpack (TR).

The control of the engine coolant flow reduces engine load. The foremost objective in this respect is reducing fuel consumption under all operating conditions, in addition to reduce emissions.