Mini Water Pump Friction Wheel Drive System

Mini Water Pump Friction Wheel Drive System

The tensioner is able to disengage the water pump until the engine has reached a specific temperature.

One of the more interesting drive belt arrangements can be found on the Mini Cooper with the 1.6L Tritec engine. The new four-cylinder engine had a surprise for technicians when it came time to replace the water pump. 

The water pump has what looks to be a belt around the pulley but is actually rubber bonded to the outside. The water pump is turned by a metal wheel driven by the crankshaft pulley – this  wheel is what transfers the motion of the crankshaft to the water pump. 

This innovative tensioner is called a friction wheel drive system. The tensioner is able to disengage the water pump until the engine has reached a specific temperature. On a cold engine that is turned off, the tensioner will feel a little loose and you might be able to turn the pump by hand.

When the engine management system engages the water pump a small electric motor inside the tensioner changes the length of tensioner. The wheel is pulled onto the back of the belt on the crankshaft and water pump pulley.

If you need to replace the belt or water pump, you need to disengage the tensioner. To release the tension, a tab first needs to be pulled out. The main problem that can occur is the rubber on the outside of the water pump can wear out or come off the wheel. This can cause noise and possible damage to the tensioner and even to the back of the drive belt. If the water pump or wheel on the tensioner seizes, it can cause a flat spot on the pulley and can also cause damage to the drive belt. Some aftermarket suppliers have improved the rubber on the pulley so it will not separate. 

In 2008, Mini stopped using the Tritec engine. 

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The ECM provides the voltage to the primary coil winding. The primary winding might have 100 turns around the coil’s core or plates. When the voltage to the coil is turned off, a magnetic field collapses. The collapsing field will generate more than 100 volts thanks to inductance. The energy is transformed by the windings in the secondary with inductance again, but thanks to the 10,000 windings, the voltage is boosted to 40kV at the spark plug’s electrodes. The best way to see inductance inside the primary windings is to use an amp probe placed around the positive wire for the ignition coil. With this setup, you can see the current ramping in the coil and the collapse of the magnetic field. 

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