Slow tire leak, only heard depending upon the rotational position of the tire?

 

TN,
do the following to save yourself future grief.
Put an amp meter on the battery in a location where you can see it after car has been locked. If you notice a draw on the amps and you hear that same noise it could be some component running when it shouldn't and will eventually drain the battery.

 

I wish it were one of those two suggestions, but it's not. It's not a mechanical noise at all; too intermittent and irregular for that. The location is quite unmistakably in the brake servo and right-hand bonnet airbag area.

Either it will break one day, and I'll know what it was, or it won't and I won't. The car spent its first nine years supplied in Ireland; perhaps there's a leprechaun trapped behind the dash...

TN

 

Aha! Forgot you are on the other side of the 'pond'.
Check out this thread in the 'other' Jaguar forum, bet its your problem:

Strange noise from Pedestrian protection airbag unit (?) (2007XKR)

 

Yes!YES!! YES!!! That's the little b'stard, without a doubt! Thank you very much.

TN

 

As soon as the poster mentioned "Geiger counter"., I knew that was it. That describes the sound almost perfectly.

It's the alarm sounder (under the bonnet airbag). My new alarm sounder arrived today; made by Fiamm, in a Jaguar box, but would you believe it has a Mercedes part number on it? The one from a 2015 Sprinter is the same, but half the price!

Admittedly the Jaguar one has an extra bracket attached to it, but it would take at least two minutes to swap the old bracket on to the new horn. Worth every extra cent....NOT!

 

part numbers please, at your convenience. Both Jag and MB?

 

The Jaguar part number is C2P26016. Mercedes part number A072657.

TN

 

Not to worry, the US versions won't have that equipped.

 

I'm not sure what you mean. I got the Jag part number from a downloaded US EPC.

TN

 

The US versions have the alarm sounder but not the pedestrian air bags.

 

Ah yes, of course. I forgot about that.

TN

 

OK, I've replaced the sounder. It's different on the UK versions - a generic Ford/Jaguar/Mazda unit.

One last question, if I may. What's the best way to trigger the alarm to check that it is functioning?

TN

 

Aim for the first pedestrian you see?

My bad... there's too much of that happening these days.

 

Could he not simply find a hill, put it in neutral and run out in front of it?

 

The car alarm? I had the windows down and car locked, reached in and popped the hood.

 

No silly, he is talking about the pedestrian impact alarm, the screams that come from the pedestrian hitting the hood.

 

Replaced the sounder, but bigfella alarm he no workee...

I guess the alarm module is unserviceable as well. I'll get round to it...

TN

 

Has the 'geiger counter' sound gone away now?

 

Indeed it has, but it had stopped, or at least I had not heard it, before I replaced the sounder anyway.