1995 Ford Contour Squeeling noise

My '95 Contour makes an annoying intermitent squeeling noise. There is no real pattern to it. It never speeds up or slows down with engine speed, it will do it randomly whether at idle or cruising. It is always the same noise. I thought it was the air conditiong pump idler so I sprayed the air conditioning clutch with some WD40 and it still makes the noise. It almost reminds me of a pressure type squeal like when there is too much pressure is built up somewhere. It has been doing this for the last month. I've had the cooling system flushed and filled and diagnosed but it's alright. SO, I ani't got no idea..........

Thanks for your help!