I have a 2002 l322 4.4 with a gas conversion. Recently ive been experiencing a strange high pitched sort of undulating whistling noise which is coming from the vicinity of the large black housing on the left side of the engine compartment with the allen bolts (i dont know what its called, engine management housing maybe?)
Its hard to pinpoint exactly as sometimes the sound stops after a few minutes, other times it goes on for an age. It is also quite loud in the passenger compartment.
I dont think its anything to do with the gas as sometimes it starts immediately after unlocking the doors on a morning.
Has anyone experienced anything like this as Its going to be a bitch trying to get a professional to look at it as its so intermittent?