2000 neon automatic has a clunk during idle

[greasyhog]

So I was sitting in my wife's car and her a clunk while the car was in park sitting in the driveway. She said it had been doing that for a few weeks now. The clunk seems to happen every 4 or so seconds while idling and is coming from the engine compartment somewhere. There is also what seems to a hissing or sucking noise that sounds like it is coming from in the dash somewhere and also happens about every 4 seconds during idle. I really haven't had a chance to look into what the problem(s) may be or if they could be connected. I am really not sure what the clunking at idle could be. I think the hissing noise is a vacuum leak I could probably hunt down when I have a chance. Any ideas?

[greasyhog]

water pump