Intermittent noise, possibly valvetrain after overheating at the track
 

Vehicle:

B5 S4, 2000, Sedan, Manual transmission

Backstory:

I was at the track on Wednesday, car was strong. Until my second session.

10 minutes in, the CEL went on and the info display showed a red coolant symbol.
I went to exit the track and by the time I got there, my instructor reported hearing a stuttering/fluttering sound, and the engine died. I coasted into the pits.

When a rolled to a stop and exited the car, the coolant appeared to be dumping out of the car. It was putting out white smoke, and coolant was pooling on the ground.

I suspect that because it was >100 degrees outside, the car had overheated and the coolant tank pressure relief valve just opened and emptied completely.

So, I tow the car home, because I don't have any G12 coolant and distilled water with me.

Next day:

I refill coolant tank with just distilled water (planning to flush all the coolant anyway, assuming that was part of the overheating in the first place).
I start up the car, a little rough getting started, but it starts up and idles relatively smoothly. Unfortunately, there is some additional noise. Intermittent, louder tapping. Almost like a piece of metal broke off and is randomly banging around somewhere.

So, I check the CEL with vag-com. I have a P1522 and P1519 (cam adjustment malfunction, intermittent) along with misfires on 2 and 6. I search the forums for the codes and it could be all sorts of things, but mostly related to sensors going bad. I clear the codes, they have not returned (while the car has idled in my garage).

I have no idea what this noise is, what could be causing it. I can't even tell if it's inside the engine or transmission, or even something else entirely.

The strange thing is the intermittent-ness of it.

It's possible that something broke on-track, triggering the fault codes for the cam adjustment, and the overheating/coolant dump was a result of that.

Questions:

If the noise is intermittent, and the car idles relatively smoothly (e.g., RPMs do not fluctuate wildly), does that rule out valvetrain damage?

The coolant pump was replaced in the last 15-20k miles, is it possible that could be making this intermittent noise?

What should I investigate first? Should I take the valve covers off and look around … or start digging elsewhere?

Use a mechanics stethoscope to figure out were the noise is coming from and then proceed from there.

Okay, I started it up again. The sound has gone away. But now I get white smoke (really visible at 12 second mark in the video): https://www.dropbox.com/s/h0d0d2vguh...ke-7-25-16.mov

I can't tell if it's oil or coolant (not sure which based on the smell).

Okay … so there is no oily residue on the tailpipe. So, I'm guessing it's probably coolant.

If it's coolant, I might have to replace the head gasket, maybe? Thoughts on that @the_duke?

Should I compression test the cylinders, maybe?

Compression test will tell you if you have a head gasket issue. Is there any oil in the coolant reservoir? Have you checked the dipstick to make sure you don't have milky oil (coolant in the oil)? It could also be a bad turbo or turbos.

There does not appear to be oil in the coolant reservoir. No visible discoloration (yet).

I'll check the dipstick for coolant in the oil.

If it was bad turbos … would it be throwing codes of some sort … or idling rough? I don't hear any whining or drilling sounds (though, idle might not spool the turbos at all).

Thanks!

Just checked the oil. No coolant visible. BUT, the oil level is really, really low. Maybe the smoke WAS oil burning.

The oil was at a normal level prior to my track day. So, possible that the oil was burnt during the track event.

OH. Derp. The oil level is most likely low because I have the front end jacked up. Derp derp derp.

On my S4 when I got it with blown headgaskets, it smoked like that and misfired. When I tore it apart, the heads were warped. They had to be machined.