Ok I've been hearing this noise for months now and it's really starting to annoy me.
I can't really tell where it's coming from the engine, but it's kind of a grinding/rattling
sound; it's only noticeable at idle. My car is a 99 1.8t. In the sound clip, it's the irregular
sound in the background. Thanks in advance!
Here's the link: http://upload2.net/page/download/8Py...sound.wav.html

 

Sounds like a water pump.

 

Well the noise has been present for about 20k now, should the water
pump have survived that long? There are not performance or
temperature issues, it just sound nasty!

 

Yeah sometimesour water pumps knock, it is commonly miss-diagnosed for piston rod knock.
It can go on like that for thousands of miles and you wouldn't notice any problems.
My advice is to buy a complete timing belt kit from ecs tuning and get all that crap done at once.