Is this the end? 98 S70 T5 knocking noise

[cmblackburn]

Hi all,
My S70 T5 has been making an awful rattle/knocking noise for the last 5-7k now. It seemed to go away for a little while when I switched from Mobil 1 10W30 to Pennzoil Ultra Platinum 0W40 European formula, but alas it is back louder than ever.
The symptoms:
-On a cool morning (~65 degrees) and sitting overnight, the car will start with a big rattle and the oil pressure light will stay on for about 2 seconds after start up. There will then be about 7-8 bouts of "tick tick tick" or rattles before it settles down to a normal idle.
-Above ~2800 RPM's to the top of the rev range, it makes a nasty rattling noise. Sounds like a rod bearing starting to work loose to me, but others have told me it could be the flex plate or something in the top end. I replaced the cylinder head about 20k miles ago with a very low mileage '98 2.4T head.
-When arriving home from any drive, the engine rattles away at idle and sounds uneven and lopey. It also sounds like the starter has to work a bit harder to start the car up again after driving it around.

Could it be engine replacement time?
I know my engine is going to need, at the minimum, sump o-rings and a new turbo. I was thinking along the lines of pulling a few bearing caps when I do the o-rings- if they're down to the brass, I'd be dropping in a 2.5T from a newer XC90. The days of having low mileage 2.3 "N" engines in the junkyards have simply dried up- there are 3 96 850 turbos currently in a yard not far from me, but I have been told by my sources these are all 200k+ cars. I want something I can just drop in and not worry about.
My S70 currently has 256,000 miles and will only keep going up as I enter the job world.
Thanks in advance, everyone. Here are some videos I have taken of the noise.

[abscate]

Sounds are always tough to diagnose over the webs, but that sounds like an exhaust leak tome, not a bottom nor top end noise. Definite not a rod knock- that sounds like a rattlesnake when you lift.

The big ends on these motors are so tough I would rule that out to the end.

[matthew1]

Agree with abscate. Rod knock is a horrible, unmistakable clatter.

I've heard it on a Ford V6.

[JRL]

I don't hear much of anything even with my volume turned all the way up
You Do NOT have any bottom end noise, you may have some mild lifter noise or a bearing going bad in one of your accessories.
You engine is basically OK

EDIT:
Listening to your 1st (and only video that lasts more than 7 seconds!!), what you're hearing sounds like older and worn valve lifters

[mrbrian200]

Does this engine utilize hydraulic lash adjusters?

[JRL]

Supposed to

[FLXC90]

I would start with the sump o-ring job, and maybe run some seafoam or similar then oil change. O-rings first due to slow build oil pressure you indicated.

[scot850]

I agree with the other guys. Does not sound like a rod issue, more of a valve lifter issue. Oil pan 'O' ring job as the guys suggest would be a place to start.

Another issue, if you have one on your engine can be the oil cooler thermostat, but it tends to whistle more than knock.

Neil.

[mrbrian200]

I concur. Do the sump seals first and make sure you're getting oil pressure. I'm not familiar with the internal design of the lash adjusters on this engine. But I would expect them to collapse if they're not getting enough oil in which case the noise would be the cam lobes sort of crashing onto the top of the hydraulic tappets at a steep angle due to excessive clearance.

I've had a leaky check valve on a hydraulic lash adjuster on a Chrysler/Mits 2.5 that sounded very close to that if it sat for a long time without being run. But oil pressure wasn't the issue so shortly after starting the engine the noise would go away and stay away.

[readallthebooks]

sounds like lifters to me too. isnt that a really common issue on these cars?