S2000RJ

I must be bored today, I just spent five minutes looking under the bonnet of my car . There isn't anything there that should be active. FWIW the air pump is under the wing. Could it be something under the dashboard?

In that area of the engine bay, you've got the brake master, clutch master, ABS and a control box, which I think is for the EPS. On my car, the alarm is ahead of the suspension pickup, but it could be mounted behind.

Have you got anything touching the black heatshield? It makes quite a loud noise if knocked. Could there be a loose label or something tapping against it in the wind? Is there anything hanging from the underside of the bonnet? Is there antything loose on the exhaust, which could rattle? Maybe you've got a friendly mouse or something moved in?

If it's not something mechanical, I wonder if it's the ABS modulator working overtime? I'm not sure if it's on a permanent live circuit. I still wonder if it's alarm related, I had something similar on a previous car, where I washed the alarm by accident You could probably rule out the electrics, by disconnecting the battery. If you do this yourself, make sure you disconnect the earth (-VE) terminal first! You'll need to re-enter the radio code if you do this!

Can't think of anything else to suggest. It sounds like it's worth a trip to the dealer. Good luck.

pete_keeling

Thanks for the suggestions - it's booked in to see the dealer next Tuesday

It's definitely not anything moving within the engine compartment. I just had a friend cast his ear over it and his suggestion was that it sounded more like a leaking diaphragm than anything (brake servo ). I can't see why there should be a periodic changing of pressure to cause this build up and release effect. Maybe if I get get bored this weekend I'll create a .wav and post that.