Hey,
I have a 1997 Nissan Altima and when it's at idle, you hear like a grumbling noise from underneath the hood. The car runs fine and there are no engine lights on on the car, but it is very strange. The noise sounds like a gurgle and is most present when you first start it. Anyone heard this before? Thanks in advance.
-Anthony

It is probably coming from one of the exhaust pipe shields. Wiggle the exhaust pipes around and see if you can locate it.

its the water pump