l have a Peugeot 306 DTurbo with the woodruff key missing from the lower cambelt pulley.The pulley is solid but l really do not wanna remove it as l suspect that the key slot in the crank shaft is damaged too.If l take the pulley off l may never be able to re-assemble it without fitting a new crank shaft which is not economically viable on a £1300 car.So is it possible to release the tensioner, slide off the belt and then reverse the procedure?
Thanks Simon

l have replaced this belt on the Peugeot 205 many times, the 405, & have noticed the 306 is very similar. But l have never done a 306.
The reason the lower pulley has to come off is (if l remember correctly) YOU MUST remove the lower plastic belt cover that is behind the pulley! & also, there is not enough space to slide the old or new belt between the pulley & the motor block. Remember, the belt is moving on a gear BEHIND the crankshaft pulley.

l recommend u pull it off anyway. Then think of a new way to reattach it. Perhaps fill the woodruff key slot with a putty = the kind that dries as hard as metal.