So took a look at the car today. Re-tensioned the tensioner (if that's even a thing) and made sure it was moving freely. Had my wife start the car and the noise was still there. Interestingly the tensioner was not moving at all as far as I could see, but the belt was moving around (back and forth) on the idler pulley. If the tensioner is tight and not moving, how can the belt move back and forth on the idler?

I still have the original belt and if was a super easy swap I'd put it back on to see what happens, but would rather not take the time to swap an old worn belt on the car. Possible I just have the wrong belt? Maybe I'll order an OE Jag belt and see what it does after that. The belt I bought is a 91" 6-rib which looks to be correct.

Unless the belt moving on the idler is a sure sign of something? Bad tensioner? Any input apprecaited. Would rather not shred a belt on my commute.

 

Don't see it mentioned but Jaguar redesigned the FEAD system because of cold temperature squeaking. On my old 2005 S Type R I complained to the dealer when it was under factory warranty and thought they would just replace the belt but it is a MUCH bigger update that just that. They went to a double sided ribbed belt and different pullies too. About $900 of parts done under warranty and I will say after that was completed I never had another sound from the SC belt.

All the part numbers needed are in the attached TSB if your interested in fixing it for good.
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Thank you so much for posting this! Seems like exactly the issue I'm having, the belt walking on the idler pulley. Since my car is N/A the fix would be a flanged idler pulley, easy enough.

Yesterday I ordered a new tensioner assembly and idler (stock style) so I'll see if those fix the issue first. If not I'll get a flanged idler which looks like it will take care of it.

Thanks again, really appreciate it. Never knew these cars had an actual issue with the accessory drive.

 

If anyone is interested, the recommended flanged pulley from Jaguar (C2C 37064) can be had from Gates (36270) for around $15. Hopefully this takes care of my issue. There are reviews on Amazon that state it fixed this exact issue on the x350s. Thanks again for all of the help guys.

 

Check the torque on the idler pully bolt.

 

Good idea, will do. Ordered the flanged pulley anyway since Jag called for the update, but definitely possible its loose hence the belt walking. Hope to get this all sorted within the next day or two. Have never had a simple belt change cause so many problems.

 

Nice find on the Gates pulley. Hope to see your problem fixed!
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I hope so too! Received it today and it was Made in Canada, a nice surprise. Will get it installed tomorrow morning and report back.

 

36270 works great on the tensioner. i forgot why but i don’t put it on the idler bracket.

 

Easy to overlook xalty, it is almost hidden.
Unless your underneath, & looking up.

 

Flanged idler pulley as per the TSB seemed to the the trick, car was dead silent on startup. Will know for sure tomorrow morning when I leave for work and its really cold.

Replacing that pulley was not too much fun. No way to get at it from the top, so had to jack the car up and remove the belly pan. Would have been a 5 minute job from there, but Jaguar decided to route a metal pipe dead center on the pulley bolt from what I assume is the secondary air injection system. Had to pry the pipe back just a bit to get the bolt out and then back in.

After looking at the accessory drive again, no wonder they had issues...There are two smooth non-flanged pulleys diretly in line (tensioner/idler), one of these should have been flanged or grooved from the start. Either way thank you all for the help and glad the car is nice and quiet again. Hopefully this helps someone in the future with the same issue.

 

Yes this was a big discussion back when these cars were newer but since they have all dropped off factory warranty that knowledge has kind of faded away. Plus the fact that jaguar released the TSB way back in 2009 I am sure quite a few cars were fixed under warranty.
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Interesting, it was definitely done incorrectly and hopefully most have been fixed. Started car cold this morning and quiet as a mouse, I'm a happy guy.

It's funny that the car was perfect with the original belt and only began to act up when I changed the belt preventatively. I guess disturbing what had been working for all those years shook something up. Glad its all sorted now and hopefully I'll never have to change that pulley again. Tensioner would be easier to replace if that ends up giving me issues in the future, but all seems to be working perfectly now.

 

Here's a short video where you can see the accessory tensioner moving creating the clicking noise on startup. With the drop in temps this is happening to both my X350s, and on the other one I did access the belt tensioner and release tension a few times, let the belt rest back into place and the clicking disappeared.