I was told by a local Jag Dealer they did not have a "jig" nor a "timing chain alignment tool" to be able replace the timing chain tensioner or the timing chain on a 1996 Jaguar XJ12. In addition it would take about 25-30 hrs of labor hours just to take the engine apart. What type of labor and tools does it take to replace the timing chain tensioner and timing chain, due to the cold start rattle and idle rattling?

 

The Jig and or Alignment Tool is their problem not yours. 25-30 labor hours total sounds about right but not to just disassemble. The dealer obviously does not want your business based on what was said above. Which Dealership? Unable to advise based on experience but would imagine a basic set of tools would suffice. It has on every other repair I have attempted on these cats. Not any more difficult than any other car just a few more things in the way is all. Do not spin motor backwards while repairing. GOOD LUCK!

 

After the dealer turned down the timing chain/tensioner work, then I took it down the road to a local jag specialist, run by 2 guys in the business for a long time. They couldn't find the cold start rattle nor the idle rattle at the time of the visit. They did an upper shock bushing instead and Bank B MAP sensor, used steth and "suspect air pump maybe noisy."
I guess on to the next, and see if it is the air pump. Random engine idle rattle, not inducive of speed or engine. Just keeps coming and going, frustrating....

I did find out XJ12 V12 only has 1 timing chain, I thought it had 4 timing chains like the V8's.

Any help on this rattling/ruddering under the hood of what sounds like the driver side during cold start or idle would be greatly appreciated.

 

Interloper here from the XJS forum. This does not sound like a timing chain tensioner issue. If it was the noise would be absolutely HUGE. Much more likely that an exhaust shield or rack heat shield, or something like that is rattling.

 

Interlopers are welcome. If it wasn't for the XJS forum not much of the XJ12 issue's would get solved. We are a rare cat/owner whose numbers continue to deplete everyday. And yet values stay flat.

 

I'm with Greg, and have NO iea what an Interloper is.

I have had a few where that Plastic Boomerang has snapped, due to some clown rotating the engine backwards.

Rattle, yes.
Engine hunting, HELL yes.
Down on oomph, YES.

Cat converters rattle, and that can be hard to pin down. Usually under the car with a rubber mallet, and tap, tap the Cats.

Air pump, maybe, we did not get that stuff, so no experience there.

An idler pulley on the serpentine drive belt, they make strange noises as they give up.

 

The air pump does make a nearly rattling sound when it runs. I don't like it but it is temporary, it comes and goes as you say. First on cold start but then on and off at random intervals while idling. Seems like the ECU is constantly testing the system when at idle.

It is easy to look at the air pump and watch it engage and disengage, if you (or the shop) haven't done that yet! The sound could be worse for you if the pump is wearing out.

Above suggestions must be considered too.

I've been known to interlope (?) into the XJ-S forum. They don't seem to mind. Thing is, I get lonely over here. I find myself reading all of my own posts over and over! The other section has approximately 100 times more traffic.

Regardless, please let us know what you find out with that Sapphire beauty.