2003 V40 1.9D Noise at hot idle

[skyship007]

Hi All,
I've just joined this forum to see if I can get any ideas as to what might be causing a noise at idle when my V40 diesel is warm. The engine idles perfectly but there is an additional chirp that is only at idle, if the revs are increased slightly it stops. The noise has nothing to do with any aux belt services, as it remained after the belt was removed. Using the clutch or pumping the brakes makes no difference. The cam belt, tensioner and water pump were all replaced last year and that also made no difference. Various experts have looked at it and no one has a definite opinion. My used oil analysis is perfect, so this is not a main block problem.
I would be most interested in any opinions as to a possible cause.