How would I know if I need the "nub' replaced. I only have 20k on the car.

 

My guess is someone trying to pull "muffler bearing" on you.

Supercharger on XKRs and early F-types had a coupler that could wear down and cause loud rattling at idle. It doesn't rattle, it doesn't need to be fixed.

 

My car is a '14 V6s and the dealer says it is on front of supercharger. My warranty and extended are over. They tried to get Red Shield to approve it in Jan. but they declined it as part was not malfunctioning. The car has had a little rattle at start up since almost new but it disappears. Jag replaced these as they came up on warranty, because I only have 20k it may be coming up so I need to know what to look for. Thanks

 

There’s a bunch of monkeys with ball peen hammers that are let loose inside the engine when it’s cold. They always calm down once they warm up. It’s been like that on my F-Type for the entirety of its 32k mile life. Tappets, fuel injectors, etc. all contribute to the fun. Start to worry when a warm engine doesn’t put the monkeys to sleep.

 

Ha ha well put lol

 

unhingd is correct, the AJ's are a loud motor in general and when cold they sound like they are coming apart..after 2-3 mins if it still makes noises you should be worried.

 

When I first got my car I was certain it had both chain slap and valve adjuster issues. It doesn't - these engines are just loud.

Still, just because you are paranoid, doesn't mean somebody is not after you.

 

I imagine by "nub" your mechanic is referring to the supercharger coupling, its a plastic part in the snout of all Eaton twin scroll superchargers. Over time the holes in the plastic become slightly worn/eggshapped and at idle it creates a rattle - sounds a bit like rocks rattling around inside the supercharger. Here is a quick write up on it, (generic -non-Jaguar specific). How to replace an Eaton Supercharger Coupler : SuperchargersOnline, Worlds largest Supercharger Resource. Get Serious About Power

As others have said, ignore noises when engine is cold, but if you hear the "rattling rocks" sound at hot idle, this could be your culprit. Had to change this coupling on my SC Tundra at 60,000 miles, took about 4 hours to pull the snout and replace. They make an improved nylon/resin reinforced coupler that is $20, or you can get the original version for $12. Usually the demise of the coupling is mileage based, and typically not a problem until 50,000+ miles, but I have heard of it failing as low as 20,000 miles. Once the noise does become noticable, I'm told you don't want to ignore it, as it can lead to more significant damage to the SC.

 

Here's the TSB for the V8 supercharger ...
https://www.dropbox.com/s/4itzi5b6rw...Noise.pdf?dl=0