My 2013 XF estate sometime makes a strange noise coming from the engine area most noticeably when driving off from the traffic lights under moderate acceleration. It sounds as if the engine does a little fart when setting off, but not every time. Two weeks ago when I collected the car after its annual service, Jaguar informed me they uploaded new engine software. Ever since then the exhaust note seems different particularly at low speeds. At motorway speed I don’t notice any difference. Last week, I took the car back to Jaguar, they secured the engine air inlet filter housing which they said was the cause, but the same day the noise was back. Does anybody have any ideas as to the cause??

 

Have you tried putting it in neutral and revving to see if it still makes the sound? That can help you isolate if it's drivetrain or engine noise.
Is there another description of the sound you could use? There are many different farts out there...
Specifically, is it a short sound? Does it stay the same pitch? Is there a clunk to it or is it more of a rubbing?

 

Good idea, I'll try the neutral rev test. The noise burst when it happens sounds a bit like a sports exhaust in overrun. I don't detect a clunk or rubbing. Noise lasts a few seconds while pulling away in lowish revs. I forgot to mention engine is a 2.2L diesel 200hp covered 16000km

 

I'd check your fans and pulleys. You probably have something loose around one of them that is rubbing when it gets some inertia. Look for something dangling in front of them.

Edit: Usually this is a fan shroud, so check that thoroughly.

 

Thanks for the tips, greatly appreciated. Oh by the way, haven't managed to duplicate the noise by revving the engine while standing still in neutral. So it must be some loose or rubbing at the front. Next week it's booked in to the local Jaguar dealer for a small paint touch-up, I'll ask them to check it out.
Thanks again

 

Would you believe it, picked up the car from the local Jag dealership last week after they checked out everything including the engine underside floor pans. First few days I didn’t hear anything thinking they solved the problem, but this week while driving to work the noise reappeared. While putting my boots on last night to take the dog for a walk, I put my hand on the front of the bonnet to steady myself. Even though the bonnet was latched, it still moved down about 1/4 inch. Pushing my hand repeatable on the front, it made a rattling noise, could this be the problem..! I adjusted out slightly the two rubber stops on the front bulk head to remove the play. I’m dying to take it for a test drive tomorrow to see if this was the cause of the mysterious noise..!

 

Here's hoping! I swear I've spent almost as much time tracking down noises in this car than I have driving it.