I had a rattle start a couple of days ago. After quite a bit of research, I think I narrowed it down to the crankshaft pulley needing to be replaced. Does this seem right?

 

Definitely looks like a bad bearing.

 

The crank pulley you are showing is the harmonic damper which has no bearing within it. It is keyed to the crank shaft with a woodruff key and just has a single 30mm M10 bolt that secures it onto the crankshaft.
Unless the bolt is loose or the pulley centre mating surface has somehow "slogged out" and is now wobbling on the end of the crank shaft due to excess clearance, the likely source of your noise will be either the tensioner idler or one to the other two idlers that position the accessory drive belt.
A tip from my dear old dad (who was a electric motor and generator winder) for tracking down stray bearing noises.....if you have a long shafted screwdriver you can put the tip onto the suspected target - in this case the tensioner arm and listen down the handle of the screwdriver to see if the noise is louder there than the center point of the other idlers. (just don't put the screwdriver onto any of the moving parts, just onto their fixing points!).
Good luck with isolating the noise :-)

 

Or...use a proper tool for the job =

https://www.harborfreight.com/mechan...ope-63691.html

 

Thanks for the pointer for the tool.
I just don't happen to have that type of stethoscope lying around my garage and assuming Muttonjohn might not one on hand either.
But being the ever keen improviser.....I do have a bunch of screwdrivers and various hollow tubes I have resorted to over the years when the need occasionally arises.

By the way Dell, curiosity go the better of me and went and had a look at one of those local 3.0 AWD X's last weekend. A 2005 Sovereign with 119,000Km (75K mls).
Engine is a bit wet around sump, trans seems to be a bit indecisive in up-shifting (Revs climb during shifts even on light throttle and it seems to have elongated transition time), exhaust is pretty thin and will need pipes replaced soon and some buffoon unfortunately fitted 60 series tyres onto the 16" allloys, so it is catching inner guards on any moderate turn.
Other than that it is pretty tidy and engine ran nicely. Suspension knock free and underside looked a bit more weathered than mine but certainly not a rust-fest!
Considering my options as to whether to upspec my choice of 2005 ride.......
What do you think about the trans with those miles, just a good fluid change to crisp it up, or am I likely to be walking into other issues with it?

 

Idk, I bought mine with 130,000+ miles. Had a CarFax with all yearly maintenance records from owners. Drove from NJ to Utah w/o any problems. Trans shifted a bit quickly on acceleration between a couple of gears and same on deceleration (not really a jerk but hard). Changed fluids, been great (more info on my thread w/pics). Rear needed front rear lower stabilizer bars. Front did the entire "a frame" (ball joint part) and front sway bar links. New tires because didn't align it from back first to front (unknown the X requires this). The ubiquitous "t" cooling hose failed and replaced. Battery died and replaced. MAF died and replaced. Fuel pump died and replaced.
Really mostly expected with age and miles. The only one that ate at me was evap leak that progressed until I couldn't clear it at all which ended being the inexpensive rubber hose from the fuel fill line to the gas tank which happened pretty soon after I cut a hole to replace the fuel pump and I had to pay an ex jag tech owned shop to drop the tank to fix a $50 part for $850.00.
All in all not really that bad and it's a great driver. I wouldn't sell mine unless something catastrophic happened to it now. Not much could/should go wrong being properly maintained. I have 144,000 on it now.
Btw, mine had a new starter and new tires put on by the dealer before I bought it. The previous owner had "Thermo'd" the rear upper stabilizer bars and it had new looking bilsteins on it.

 

Idler pulley. You want to replace it ASAP -- when it fails, it will wreck the drive belt and may let the engine overheat.

Mechanic's stethoscopes are simple, inexpensive and should be one of your tools.