Volvo: Intermittent rattle, peter humphrey, wheel bearings

Question
After owning two Volvo 240GL Estates and doing most of my own repairs, I recently purchased a 1988 Volvo 760 Turbo Intercooler Auto Estate and would be grateful for your help in diagnosing a "rattle" type noise which is very annoying.  It is often (but not always) present on start up and often present for around the first 5/10 minutes when running, but not always!  It is only present when the engine is running, but is not dependent on the vehicle being in motion. The noise appears to come from the passenger side front quarter of the car and initial diagnosis suggested the alternator.  This was however replaced along with the alternator drive belt but the noise persisted. Attention then turned to the air conditioning compressor (this was not operational when the car was purchased - one pipe, inlet or outlet, had been removed - reason unknown).  The compressor was still being driven by the drive belt and this was removed but the noise still persisted. I have no current plans to make the air conditioning system operational.  Wheel bearings and brake discs can be ruled out as the noise is sometimes present when the vehicle is at a stand still. The car generally is in exceptional condition for the year and the only currently known mechanical problem (besides the rattle) is some transmission noise present when accelerating in lower gears - I don't think however that this is related to the rattle.  I have checked carefully to ensure everything that should be fastened down is secure and am now running out of ideas.  I don't know if your expertise runs to 760s' but any suggestions or advice would be most welcome.  Oh, by the way the car is right hand drive.

Regards

Peter Humphrey
humphrey@beeb.net

Answer
My first thought without knowing more about the nature of the rattle, I would suggest looking at the exhaust.  Generally, you can get rattles along the line against various parts if something is bent out of shape, or if the rubber suspension for the piping has worn out.  One thing to test, does the rattle happen at all RPM's while sitting still, or does it disappear at higher RPM's?