When out to garage this morning and heard a strange clicking fingers noise from under my bonnet. Car has been parked up for this week as roads all salt, no issues and trickle charge on. Opened bonnet and the sound seemed to come from under the cover behind the coolant bottle mine been right hand drive. Under the cover is the is the brake fluid holder and a round cylinder with airbag on it arrow in picture.The noises seems to be coming from this cylinder, if i try to cover it with my hands it covers the noise a bit. Started the car a let warm up for half an hour but still there. Noise is pretty loud, you can hear it from about 2 meters away. It is a regular click of about every 3 seconds. Any answers to this welcome. Don't see any thread on this odd noise. Is this called the Pedestrian protection airbag unit, can i disconnect it without any issues and see will it stop the noise, there seems to be a wire with connector at the bottom of it.

 

I would pick up a mechanics stethoscope from HF first and pinpoint the noise better. It's only $4.49


Mechanic's Stethoscope

 

I'm pretty sure that North American X150 models don't have the Pedestrian Protection system.

It appears that the UK values the lives of pedestrians more than we do on this side of the pond.

 

Thanks guys, found this thread on another site, would this be the answer,
Strange noise from Pedestrian protection airbag unit (?) (2007XKR)

What is a Geiger Counter and what has this to do with an alarm.

 

That 'alarm sounder' sounds like your problem.
Geiger Counter - device to detect radiation (you probably don't have one, unless you've got a Mr. Fusion under the hood/bonnet). :-)

 

Still noise today, but seems to stop and come back. Seems it is the sounder under the airbag unit. Done a bit of head scratching and decided to go to the local hardware store and get some fireproof soundproof insulation. I packed it under the cylinder and area around it, making sure not to cover it. Noise can only be heard now if i put my ear down to the bonnet and is very faint. Hopefully it won't get louder that i can hear it standing by the car again.

 

As you suggest kj07xk seems my alarm sounder is gone. Left the boot open, then the door, then the bonnet and no alarm noise to show something was not locked. The unit is under the pedestrian airbag unit.
Went into my x150 service disc and it shows how to take out the passenger airbag unit and the alarm sounder.

Question 1: If i loosen the 4 bolts holding the PAU can i just lift it out of the way not disconnecting. It should not deploy as the sensor at the front of the car makes it do so that under impact, don't want to be put in orbit.

Question 2: When i disconnect and remove the anti theft alarm sounder will i get dash light of locking problems. Car opens and locks as is.

Can't seem to see one of these on any site, will probably need the part number.

 

The link you referenced above seems to answer most of your questions:
1. Disconnect the battery and let residual charge drain.
2. No warnings if disconnected.

Don't know about clearance of the PAU, we don't have them on this side of the pond (pedestrians are expendable ).