whistleing noise
 

Hello,
I have a Concorde LXI 3.2L that makes this weired whistleing noise when the engine warms up and only when its warm outside. I never recognized the noise in the winter. Does someone has any idea where it comes from or what it cause? I asume its the intake manifold but I am not sure. I thought first it might be the intake manifold gaskets but I changed them last summer and the car is still whisleing. I appreciate every help.

thanks