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2.6 - Supercharger Idler Pulleys ( Paul Stow,  December 1, 2001 )

The supercharger drive belt on XJR models runs over a fixed idler pulley, mounted in front of the thermostat block, and an adjustable idler pulley mounted directly on the front of the engine.

The adjustment is done by a movable pulley, sliding up and down on a threaded bolt. The top of this bolt can be seen from the right hand side of the car, point upward at a 45 degree angle just in front of the engine block. The head itself is just a squared off shaft, but can be turned with a decent pair of pliers.

These pulleys have been known to seize, thus throwing the drive belt. However, in itself this doesn't seem to cause any damage and, apart from significantly reduced power, the engine will continue to run without even illuminating the Check Engine light.

To remove the supercharger belt, first release tension on the belt with the adjuster.

Loosen the four fixing bolts which locate and hold the adjuster. The adjustment itself can now by turned, anti-clockwise to move the pulley down and release the tension. A good few turns are required, and a gentle tap on top of the pulley may help it to move initially. Once loose, the belt can be removed.

The idler pulley's can be removed simply by undoing the central fixing bolt. However, on the adjustment pulley it may be better to remove the mechanism as a whole by undoing for four fixing bolts. This will allow the pulley to be removed without straining against the adjustment bolt itself.

Refitting is the reversal of removal. The pulley bolts need to be tight, but not excessively so. Make sure


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