Strange 'explosion' in my Vestra 1.8 Design

Yeah, you bought a cheap knock-off copy of a Vectra...

Minor Petrol leak in a hot place?

Easy, that's your last vestage of manhood escaping out of your life.

Were you by any chance close to an airport runway when it happened?

Biggles

Thus spake Merryterry ( snipped-for-privacy@fsmail.net) unto the assembled multitudes:

Do you feel any change of air pressure, or is it just a sound? Does it happen anywhere in particular like the same stretch of road? Perhaps it's a small patch of changed road surface (e.g. a repaired patch) that makes a sudden, brief change of tyre noise?

Thanks your interest rather than the piss take of others.

No it is definately not road noise. It is a definate sudden and explosive change of air pressure in the car and you can hear a noise like some flaps in the air inlet system are suddenly closing and then instantly re-opening. I wonder if it could be an intermittent failure in whatever drives the ducted air direction operation?

Merryterry

someones tired

AC Compressor / Fan wotsits wobbling about on mount and suddenly hiting some reverberant metal when it's turned off?

Thus spake Merryterry ( snipped-for-privacy@fsmail.net) unto the assembled multitudes:

I know the feeling :-)

My car's an Astra, and although a Vauxhall and with I expect some similarities of ventilation and a/c, I've never experienced this problem. Might be worth seeing what happens if the windows are left slightly open. If it's a cabin pressure thing (sounds a bit silly; it's not an aircraft after all!) then with the windows open it should prevent the problem. The fact that it seems to happen so infrequently doesn't help, though. Would be worth noting time of day, weather conditions, location, speed etc each time it happens, so as to look for similarities of condition or circumstance.