hi ,i have a 2001 disco 2 td5 been having trouble with the battery light coming on , its not all the time but when it does it drains the battery and stops the car within a mile . i got it home after a jump start the alternater looks oily so sprayed wd40 on it and gave it a tap with a piece of wood was fine for a week now its started again any idea where the oils leaking from its so hard to see and do you think a new alternater is needed any help please regards arv