how do i replace the fan belt on a peugeot 205 gti?

Slacken off the alternator bolts, swing the alternator in towards the engine, put the belt over the pulleys, pull the alternator away from the engine to tension the belt, and holding it in place retighten the bolts. Tension should be ok if you can push the belt about 1/2" and its lonest span between pulleys.

Chicks Fan
December 2008