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Discussion Starter · #1 ·
Hi all, this is I my first post since joining (located in Denmark). I've owned my 2008 XF 3.0 petrol for little more than half a year now and as I'm getting to know it, I've noticed a few peculiar sounds.
First of all, when reaching around 10-15 mph after a standstill/cold start, there is a sound from under the bonnet - slightly crunchy in a mechanical way as if something is locking or moving into place. An almost similar sound can be heard when the cruise control is activated and the car slows down. The third odd sound appears to coming from the left front brake after driving for about 5-10 minutes, it's almost like the brake is pulsing with a few seconds intervals - usually 5-6 times before it stops. What are these sounds? Are they normal?

Br

Ulf
 

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Welcome to the forum.
I have not idea what your problem may be. Unfortunately these under the bonnet noises as you've described them could be just about anything.
How good is your hearing? Could the noises be comming from elsewhere? I know that fokls have been cought out before when they think noises are comming from one place but it turns out to be from somewhere completely different.
When you described a noise at 10-15 mph, my mind emideately thought of the auto locking of the doors, but if you're convinced it comes from under the bonnet, clearly it isn't that. As for the other two sounds, no they aren't normal, so get them checked out at next service.
Sorry I can't be more helpful.
 

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Discussion Starter · #4 ·
Thanks for your reply, I've just switched to auto-lock when driving and the doors locking corresponds with the sound from under the bonnet - at the same speed, so I guess it's something locking (perhaps the bonnet), the second sound from the cruise control needs investigating (perhaps an actuator?) and regarding the third, I've heard XF-owners talk about a brake heating cycle, where the car brakes slightly to heat the brakes - sound a bit far-fetched, though... :) Br Ulf
 

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Discussion Starter · #6 ·
It's like a buzzing from the right front wheel, as if the ABS pulses (no vibration in pedal, though) briefly 4-5 times with a few seconds interval, then it goes away. It's always after driving for 4-5 minutes when starting from cold, never when the car is already warm. I've heard people mentioning that the car heats up the brakes automatically, but it just seems weird and slightly concerning... :)
 

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I don't think I've ever heard of a car automatically heating it's own brakes. If Jags do this, then it's new to me. It would be worth knowing if the car is throwing up any codes. Does the car make the noise if started from cold but remains parked and doesn't move, or does it make the noise only while moving? Also, the next time you're out in the car from cold, and you're approaching the time when the buzzing usually starts, turn off your air con/ventilation completely and see if the sound still occurs. You should also do a thorough visual check of the wheel assembly (inc. tyre pressure). Apart from this I can't think of anything else to do other than throw money at it by booking it into a garage. Those with more experience may be able to suggest other things but I'm like you, out of ideas at this stage.
 

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Discussion Starter · #8 ·
The reason I think it has to do with heating is that the sounds/pulses from the front brake are heard more times when it's colder - today it is 8 degrees and it only did it 2-3 times whereas it did it 6-7 times when it was much colder (-5) a few weeks ago. It only does it from cold and turning the ventilation off didn't matter.
The crunching sound from under the bonnet appears when I reach around 10 mph, a bit sooner than the auto-locking doors whether the car is cold or not, my guess that it's some kind of actuator that either locks the bonnet or activates the under-bonnet airbags...

Guess I'll run it by a garage, but your input has been much appreciated :)

Have a great weekend

Ulf
 
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