Hey guys, I'm new to the forums as I'm a new Jaguar owner & I'm hoping for some helpful insight from some other jag owners. So from what I've collected after reading around on the forums/google.. I'm assuming this is not a cheap repair. From under-the-hood, something is making a less than healthy sound, and I'm not a mechanic by any means, but could this be the timing chain tensioner I've heard so much about? If not, any ideas on what it is & what I could expect? I'm located in Maryland if anyone has any ideas on the best place to take my car for service, or if this is (possibly) a DIY fix I could have one of my more mechanically-inclined friends/family members take a look at?

Here is a quick video of the noise I recorded earlier today while the car was running with the hood open.
https://drive.google.com/file/d/1CPf...ew?usp=sharing

 

First we'd like to welcome you Charlie. Please introduce yourself and your Jag in the New Members Forum...top left, Forums, New Members Area.
Like any automobile, diagnosing a noise can be difficult. But from what you've posted it could be a couple of things. From either a bad tensioner situation as you suspect to a bad wrist pin amongst others.
You can somewhat easily remove the cam/valve covers without much mechanical skill and inspect the chains and tensioners from above. Checking for looseness and broken/damaged parts. There are also a number of members in your area, so if you post here, you may also wish to post in your Regional Forum regarding a Technician if you so desire to use one.
In my signature you'll see a "How To" link, prompt it and look for Tensioner Replacement by Blackonyx to review the process of a complete primary and secondary tensioner, chain and guide replacement. Many members have accomplished this on their own (myself included 2 yrs ago), you just need to decide if you wish to handle it. That is if this is your issue?
Keep us updated and I know there will be some other input from knowledgeable members.

 

Here's link that will be very helpful for future endeavors...JagRepair.com - Jaguar Repair Information Resource
You'll also be able to make use of this (X308 Workshop Manual)... https://www.jaguarforums.com/forum/x...al-pdf-183893/ ...what nice is in the Table of Contents when you find what you want, just move your mouse over the section and prompt it and it will go to it vs. scrolling down 2500 pages.

 

Charlie, I suggest you don't start/run the car again until you've inspected the timing. As already suggest by HH the removal of the cam covers is a relatively simple task.

I say don't run it because the noise sounds very much like an unsupported timing chain, starting the car at this point is like playing Russian roulette with it, they're an 'interference engine' meaning if the timing skips it will likely destroy valves and pistons.

Don't start the car until this is confirmed.

 

After the timing chain /guides inspection paint white a mark across the harmonic balancer and see if they stay aligned after you test drive then after that easy test pull the belts off one at a time as I assume there are two to split the problem in half .With some running limits for unpowered items like waterpump .

https://www.jaguarforums.com/forum/x...ptions-157430/

Double check advice needed if that is advisable

 

I will be taking my XJR to the jaguar dealership on Monday to have it looked over, but since the Jag dealership will surely be more costly we will probably be taking it to a shop nearby that we've used before & a good experience with. I'm hoping the scope of the issue ranges no farther than an aging timing chain/tensioners.
Also, would anyone be able to give me an estimate of how much it normally costs to get this timing chain replaced? Isn't it also normal for the tensioners/water pump to be replaced along with a new timing chain? Are there any other things I should be replacing as I near the 100k mark?
Thanks in advance for anyone who takes their time to help out!

 

Thermostat and thermostat housing should be replaced if not metal. Yes a new water pump wouldn't hurt, your there after all and it has to come off anyways. If not done, new plugs, the valley hoses are a must.
I seriously think you can skip the dealer and go to the inde'. Your just asking both doctors the same thing and well, paying twice for the same answer.
Don't be afraid to remove a cam/valve cover to see for yourself. Take off the center piece (8mm heads), remove the coil packs, may as well pull the plugs and check them. Then undo the cam covers outer bolts (10mm I recall), and it will come off for you. I feel the passenger side to be the easier side because once you remove the airbox and tube to the TB, you have plenty of space.