Taz_devil

Hi guys, I hope this is the correct subforum for this topic

This is my second post here, I have recently bought a 2001 wrx with pretty high kms (264 000)

I had it all inspected by my usual mechanic shortly after purchase, he gave it a clean bill of health, besides new tires and a CV shaft.

All seemed to be fine, no boost leaks (I thought there was initially, turned out to be a dodgy cheap gauge) and the car performed well with no issues

I noticed a week or so after purchase that it made a subtle TAKing sound at idle when cold. This went away when warm, and was only under light throttle. I figured this to be piston slap and all was well. Recently, I went on a long trip of about ~600km total. When I arrived at my destination, I noticed a harsh, rattley metallic scrapping sound at idle. This sound was intermittent and wasn't related to engine speed. After a few light blips of the throttle, the sound seemed to 'clear' and go away. The same occurred when I returned from this trip.

Also, during and after this trip, what I thought was piston slap has definitely gotten worse. The sound is more steady, slightly louder and almost always present at idle, low revs and sometimes also when hot. Sometimes it disappears, usually around the time I am trying to show someone to get a second opinion :P I have listened to countless videos of piston slap, lifter noise and the dreaded spun bearing knock. It is the latter that I am afraid of.

I took the car down yesterday to see my mechanic, he couldn't hear it when I pointed it out. After a short drive and popping the bonnet, he did hear it and said that I have an exhaust leak and perhaps some lifter noise that he can take care of at the next service. This eased my mind a bit, as I figure he would have heard all these sounds before and if it was a worst case scenario, he should know.

Today though, I'm having second thoughts. I don't think it is the lifters, as they make a ticking sound (which is also a sound the car makes but I'm not so concerned about this), the sound I am hearing sounds more 'wet' and like a 'clock clock clock'. It sounds so much like a spun bearing from what I can tell, and it is getting worse. The other, scraping rattle sound I believe could be an exhaust leak, as it seems to come from near the heat shield and I can smell exhaust gas in the engine bay. This is not so much a problem for now, as far as I can tell. I am terrified of driving it, but I sunk all my money into the car and have no alternative. Is there any way I can determine, for sure, the source of the knocking sound?

I don't have a way to record a video for diagnosis atm, but I can tomorrow. Taken from someone else's video, it sounds a lot like this, particularly at the end when he gives the throttle a blip. https://www.youtube.com/watch?v=LCmPbRUMaks&feature=youtu.be
at 3:00 into the video