About a month ago was the last time I checked my coolant level. It was normal in the reservoir and the car was working fine. Over the last few weeks, the car ('04 WRX) developed the gurgling/bubbling noise that seems to be characteristic of low coolant and/or air in the system. So today I finally got around to checking it, the reservoir is basically empty. I haven't been able to visualize any leaks and there's at least some coolant in the radiator.
I've read through the coolant FAQ and a ton of other threads and have run across a few replies where people suggested some serious problems as being the source. I've also had a pretty constant knocking/pinging problem that Subaru is still not dealing with.
So, obviously I'm still doing the dealer thing and battling it out with them, but should I be requesting a compression test, emissions test, etc.? I just don't know what's up with the car and the relatively fast loss of coolant. I don't want to get the brush-off by the dealer again, so is there any other good info I should know about going in with this new problem? And what could cause coolant to drop way off like that (including horrific engine problems)?