Trying to figure out what's going on with my car. 2005 Pontiac Vibe with 195k miles (I've only had it since 182k). A few months ago I noticed as I was idling at a stoplight after having just gotten off the interstate a "thunk thunk thunk" sound. I immediately worried it was an engine knock or something bound to cost way more than the car was worth so I pulled over and popped the hood and didn't hear it anywhere. As I investigated more, I realized it was coming from "inside" the dashboard on the passenger side, kind of behind the glove box, but it was not audible from under the hood.
Since it didn't seem to be running funny and it wasn't coming from the engine, I disregarded it and have driven it that way for a while, it's not noticeable when driving but as soon as you're idling you hear it, and it seems to be more noticeable after having been driven for a while at higher speeds (or it could just be that I'm more aware of it after the highway noise has died down). Not so long ago, as I was trying to isolate the sound again, I discovered that it still occurs if the key in the ignition is turned to "on" but the car isn't running. (as in, past the point where you turn the key just to get the lights/radio on, and far enough to get the fan on, but not to actually turn the engine over).
It makes a sort of low-key "thunk....thunk....thunk.............thunk...thunk..............thunk...thunk..." But it's not a clunking/knocking sound really (sounds are hard as hell to explain).
I have absolutely no idea what it is, but today it seemed to get much louder and 'move' more toward the center of the dashboard. I'm wondering if it's just something to do with the fan for the cabin that's unimportant or if it's something that I need to get checked out pronto.
Thanks for any insights.