This question has been eating my brain for a few weeks now. When i drive i hear water slushing around. for example if you take a water bottle fill it up half way and shake it you hear that sound. well i hear that when i take off, it comes from the glove box area. i check for leaks and i don't see anything. i hear it when the heater is on. or defroster. sometimes i will hear a noise that is unexplainable. it sounds like little pieces of rock in a plastic bag. it will sometimes make a smell of coal. once a little piece of coal fell when i heard that noise. i looked up there and couldn't find anything. Does any one have any idea what this is?

its really annoying driving around sounding like your driving with water in your truck.

i hear both noises mostly when i am taking off.