I purchased a 2000 XJR new in 2001. I am not driving it currently but it is still in the family. My son reported an intermittent noise issue with it recently and sent a video clip including the disturbing noise. To me it sounds like a light duty jackhammer working. I personally have not been with the car to witness the issue first hand. Perhaps later this coming week I will get a chance to drive it. For now, I am simply bringing it to the Forum's attention to see if anyone else has the same experience or can shed some light as to the cause. The video is posted on my YouTube channel and I did provide a summary writeup there with a few details eg. Battery is charged. Noise occurs whether car is being driven or in Park with engine running. Hope you can take a look.
And thanks.

 

Does the sound get louder with increased RPM? That's an odd one. But I'm sure we'll be able to help you track it down.

 

Have the secondary timing chain tensioners been replaced?

Check the oil level?

I’ve seen many plastic timing components clog up an oil pickup screen and cause low oil pressure before. It sounds like a top end noise.

How many miles are on it?

Just some things to think about.

 

Vehicle has 171K miles. On YouTube I incorrectly specified 165K miles. But for this issue, I don't think 6K miles makes a difference.
The timing chain, plastic tensioners, and related parts were all replaced at 144K miles back in 2014 by Indy mechanic.
Oil level is at max where it should be.
I was with the car this past Sunday but there was no noise after a couple of minutes of driving. Could not stay with it longer due to other commitment.

 

I did not mention a recent repair because I was not sure if it was related to the current noise. The recent repair by my indy mechanic was to replace the power steering pump and related parts. After experiencing the noise problem, the car was brought to the indy mechanic again. His diagnosis was that the power steering pump had started to wobble on the shaft and that was the source of the noise. He replaced the pulley and is confident that the noise problem is eliminated. And the best news is that there is no charge since the car was still under the previous warranty work. Sometimes we get lucky. Thanks to those who reviewed or offered comments.

 

I meant the power steering pump "Pulley" had started to wobble.