My 2002 3.8L non-supercharged is making a low-pitch irratic squealing noise which sounds almost like a bearing at idle, after it runs a little while. I thought it was a water pump but the noise is coming from the other end of the engine, near the upper coolant elbow. The real odd thing is, I happened to take the oil fill neck off while it was running (it took a gasp of air when I did) and the noise stopped. When I put my hand over the fill neck, it pulled some suction and after a minute or so the noise started.
My first thought is that it could be intake coolant related, but I will say the LIM gaskets have been replaced with the aluminum ones and the Dorman upper kit was installed, about 2 years ago now. It doesn't seem to be using any coolant, and the engine oil looks ok to me.
Any ideas? Could something be causing it to pull excessive vacuum in the valve cover area? And what noise could that cause?
Scratching my head here. 123,000 miles now by the way.Appreciate it!
