I have a loud engine rattle like there's a golf ball bouncing around in the engine. So far the mechanics have no idea where the knocking is coming from. Here's a video of the sound at idle. If you attempt to drive (or rev above 1500rpm) the sound becomes very loud and is then obviously undrivable.

Car has 260,000km or 162,000mi

Volvo V70 Engine rattle - YouTube

Listen for the fuel injectors and the lifters. Under that there is a low, steady *Knock*. There is also a louder bang that is irregular. It sounds like I'm hitting the camera or the car but it comes from within the engine! First it's irregular then catches up with the engine speed. Any thoughts on what those noises might be?

I was just beginning a road trip and all the fluids were checked.
Engine has appeared to be fine for years.
I pretty much only use Shell silver grade gas.
I had filled up the tank 100 km prior.
I had just changed the oil and filter 200km prior.
Symptoms appeared as I was pulling on to the highway for the first time that day.

As I accelerated on to the on ramp (with four passengers) the oil pressure light came on.
5km after that I thought I heard a low oil ticking so I pulled over to check and as I did, the engine really started knocking and whining.
Checked the oil and it was full and later I found out there was pressure. Coolant was okay too.
Turned the car on and oil pressure light never came back on.
No check engine light.
As I tried to get off the highway the knocking was so bad I could barely drive it. Probably should have left it. Got off the highway and called a tow truck.

The mechanic has drained the oil and found metal filings. He checked the timing belt and it is fine and hasn't slipped. No idea yet where the sound is coming from.

I'm hoping to find a similar experience to help me determine (where the noise is coming from and) if I need a new engine.

 

Probably going to need a motor. Metal filings in the oil and a loss of oil pressure isn't a good sign. It doesn't sound exactly like a rod knock, but it's hard to tell with a recording.

 

To be honest you probably lost oil pressure trying to get onto the highway and spun one if not all rod beaings. That sound is not good at all and you running the engine is making it worse. I'm my opinion you are going to need a new engine.