Hello gents,

I acquired a 2003 XJR last year and have been getting it ready to drive for spring. The car had sat for a few years and needed some things, but is overall in excellent condition. It has 123,000km.

This month I serviced/replaced:
Belt tensionerLF wheel bearingLF ABS sensorA/C drive beltA/C belt idler pulleySupercharger beltSpark plugsCoolant flushOil changeTransmission filter & fluidDifferential fluidSupercharger fluid
The car runs great but has a concerning rattle on cold starts that gets louder when I put the car into gear (D or R). It quiets down and runs smooth once up to temp. I'm thinking I have a bad timing tensioner despite this supposedly having the later updated version.

Which brings me to my other question - I was shopping for a timing chain, guides, and tensioners kit and there are two versions. The first is for cars up to engine number 010812999 or chassis number F59525 (1998 to Aug 2001) and the other is for cars with engine number 010813000 and above or F59526 and above (Aug 2001 to 2003). Now my car is a 2003 "model year" but it has a build date of April 2002 and the chassis number is F55507. Now obviously that number comes before F59525, hence my confusion. How can my car be a later build date yet have an earlier VIN?

​​​​​​I haven't been able to get the engine number because it's so hard to see under the car. I'm going to try again today. I'll try to get a video of the cold start noise as well. Any input would be greatly appreciated.

 

look at the engine number or pull the valve covers the vin has nothing to do with it

 

If you pull the left front wheel off, you can get a visual of the engine number, its on a rib on the engine block and you can see it if you lok past the shock into the engine bay. Mine was very hard to read so I just took a bunch of photos and zoomed in on them until I had all the numbers. My 01 is an early production from that model year, but it has a replacement engine that was made after the tensioner changeover date so I lucked out. Its entirely conceivable that your 03 could potentially have a replacement engine from the earlier AJ27 production run (as unlikely as that might seem), so your best off to collect the right data and make your plans from there.

My 01 has a piston slap sort of noise when its cold. I don't hear it while idling in park or neutral, but if I put it in gear its apparent and it goes away on its own in about a minute or so of driving. Been doing it since i biought it last year, 19k miles ago. Best thing to do is as you say, make some recordings but also to replicate the situation you hear it under and then get under the hood while its making the sound and locatize where its coming from. Might have nothing to do with timing chanis at all, or that might be it. The newer metal ones can wear out too.

 

Yeah I can see where the number is, it's just hard to make it out. I need to get a light in there and try to get a picture like you suggest.

Yes that description of the noise is pretty much spot on to what my car is doing too. And it's only on cold starts. If I drive it, park and then start it up while still warm it doesn't make the noise.

After some further research it seems the parts I was looking at are just incorrectly advertised. I found this VIN guide (see below) someone who worked at a Jag dealer posted here in the forums. F59525 is the last of the X308s. Chassis made after that would be 2003+ X350s with the 4.2 V8.