N Reg 208d Van
 

Recently when starting up my van for the initial 3-4 seconds the oil light stays on and its rather noisy, well this morning as usual this happened again but louder and for longer, whilst driving it was fine however when i stoped at jusnctions and lights the oil light came on and was hideously loud until i set off again, I have just dropped the oil and put new in, the problem is still there any help would b much appreciated Thank you