in the last few days the car makes a strange sound in the engine when it starts up. lasts only a few (10-15) seconds and then goes away. i will take to local shop this weekend.

i am sure diagnosing via sharing an audio file might not be the best approach but thought i would post it anyways in case people have an idea.

the noise is coming from almost the exact center of the engine ... maybe a bit towards the front but not much.

 

Power steering rack or pump? Can you feel anything in the steering wheel? Do the front wheels try to change position?
That's a horrible noise.

 

i do not feel anything in the steering wheel. i did not see that the wheels were trying to change. i'll look for these signs a little closer when i start it again later. a friend who listened to it last night thought it might be a belt tensioner.

 

So it wasn't the belt tensioner? Did you eliminate it as the suspect?

 

sorry. not eliminated. i should have mentioned it in the initial thread that this is one of the working theories.

 

The squeaking noise at the end caught my attention. Sounded like a pulley going bad. The thumping noise at the start might have been the tensioner reacting to the stuck pulley? In any case, get that poor baby to the car doc asap.

 

Tensioner is a good guess - it’s something that is periodically storing and releasing energy, like a stuck tensioner might. Can you observe the belt(s) in front and is there any jerking type motion in sync with the noise? I do hope it’s not the timing chain (does the timing chain have a tensioner, anyone?).

 

Wow, that is not a good sound. Please keep us updated.

 

here is the diagnosis from the jaguar shop I took the car to (direct quote cut and paste)thanks for the input.

 

At least the problem is addressed now and youre aware what youll need. I guess the next question is will you be doing the work yourself? If not I hope you have warranty although im unsure if warranty would even cover that, best regards mate!

 

I am not doing the work myself. i'll leave that to people who are way more competent than me

 

Hows your history on this car? by that I mean reliability has it been a PITA? I really enjoy XK's I personally feel like they look like modern cars like no one could tell your car is from 07 unless they personally know about Jags. I guess only age scares me of the car but I have an 12'XF and a recent purchase at that and its been solid for a year and 3 months now so age shouldnt really scare me that much just scares me that the fact IDK how to work on a car let alone a luxurious/foreign Bad B***h like these.

 

I just purchased the car in august so others with longer ownership would be in a better place to comment. from what i have read online these are quite reliable beasts and the jaguar specialist shop that is working on the car also said the same thing. of course jags seem to be know for their electrical eccentricities

 

final update ... so the mechanic replaced a few belts and the tensioner. the diagnosis turned out to be correct, a spring inside the belt tensioner had in fact failed. all good now.

 

I came back to this thread after starting my car this morning and hearing the exact same sound, right down to the fact it starts that tell-tale belt squeaking as soon as the more prominent sound stops. Thank you for confirming the cause, so many times these threads don't get seen through to completion.