Hi, i have a 300 tdi disco on an N plate, an the alternator nut keeps coming loose on it, once the nut come loose it causes damage to both the pulley and the shaft from the alternator resulting in having to replace the unit! this is now the 3rd time in 6 months it has done it!! i have checked and checked that everyting is running in line, i have tightened the nut with a big bar and put alot of locktight on the nut and the shaft from the alternator and left over night to set before installing the unit. I have also replaced the fan belt and the tensioner as i though the tensioner had a whisper of movement in it!! it just seams to do about 2000 miles and then goes again its extreamly frustrating and expensive as its a new alternator every time!! has any one had similar issues??