I recently started hearing a clattering sound under the hood at idle from my 2013 XJL Supersport. I feared it was the supercharger coupler announcing its retirement, but further investigation with a mechanic's stethoscope revealed it was the supercharger tensioner pulley that was making the rattling noise. Upon removing this from the car (pull the intake plastic and then two easy bolts), the bearing presented being loose and dry- no surprise after 100k miles and I believe Land Rover even issued a TSB regarding this issue.

Jaguar wants you to buy the entire tensioner and pulley (AJ813574) as an assembly for near $200, but the pulley itself unbolts from the tensioner assembly. It's not sold separately by JLR, but this smooth, plastic pulley has the following dimensions:
OD: 90mm
Width: 30mm
ID (inner diameter of the shielded bearing): 16mm

I searched many parts catalogues and forums but couldn't find an aftermarket replacement that met those exact specs, until I did. The part is Febest 2987-RRS. Replace this for ~$15 and you can reuse the tensioner. I'll report back how it fits when it arrives later this week, but I reverse searched catalogues with that part number and the dimensions are the same.

In the process of uninstalling the supercharger belt tensioner, I accidentally breathed on some of the plastic coolant pipes and they sprung a leak, so I'll be replacing the coolant overflow hose (C2D6362) and upgrading the feeble-looking water pump outlet nipple to a brass part (cannot add any hyperlink on my first post but they are all over Amazon and eBay).


pulley

 

Good find and thanks much for the post, picture and description of the part.
Hope to hear it works well too.
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When I replaced my belts, mine was definitely on it's last legs. They ARE sold at Rockauto and are listed as interchangeable with the accessory drive idler. What is curious is that they are 17mm id on the bearing, not 16. Funny thing is that I HAD a steel one from a Mopar, which fit (ie, dimensionally identical i.d., o.d.,, but 2mm wider). It TOO is listed as a 17mm id. Are you SURE on that 16mm measure? The Dayco number is 89828.

 

I installed the Febest pulley today. It appears to be the same quality as the OE item and at $13.86 shipped, a whole lot less expensive.



Stock part on top, Febest pulley below.

 

Yep, 100% sure. The supercharger tensioner pulley (#3 below) is 90mm in diameter and the Dayco #89828 is only 70mm.

Unless you are saying the Dayco part is the equivalent of #4 in this diagram?

 

Update- Dayco #89828 is definitely not a replacement for #4 in the diagram above. On my 2013 XJL Supersport, the belt that drives the supercharger has ribs on both sides and is an 8-rib belt. The Dayco part number has only 6 ribs.

JLR switched around the belt and idler designs a few times on the supercharged motors; some of these belts are ribbed on two sides and some are not. If the belt is ribbed on both sides, the idler is also (but not the tensioner). The OES replacement part number for #4 is C2D21157. The bearing ID is 17mm and the outer diameter is around 92mm. URO Parts makes a replacement pulley with an NTN bearing for just over $40 that is an acceptable replacement. I have not found another suitable aftermarket replacement for this pulley in the Dayco catalogue.

 

I found this thread and had the question that you just posted about.
I'm running the double sided V belt from VelocityAP and I have a smooth drive belt tensioner, and a ribbed idler pulley as well as ribbed everything else.

I was getting really confused why multiple parts said they fit the 2012 XJ line with both smooth or ribbed drive belt tensioner pulleys. It sounds like smooth is correct for my car.