Got a Corsa here (1.2L N-reg, 89K, regular services all its life) which seems to have developed a strange periodic noise from the engine.
At idle it sounds like a cross between a metallic scraping and a rattle which comes on every 5-10 seconds, then fades out again, lasting for maybe a second (i.e. not a noise happening directly at engine speed). If I rev the engine to say twice idle speed the noise is still there, and seems to occur slightly more frequently - but nothing like twice as much as at idle.
It *seems* like it's coming from the cambelt end of the engine - I wondered about the alternator being on its way out, but I just checked that by taking the drive belt off and the noise is still there.
Tomorrow I'll try taking the cam belt cover off I think (assuming it can be done without removing the alternator drive pulley from the crank) and see if that makes it any easier to pinpoint.
Sound at all familiar to anyone, though? It seems weird to me that it's such a relatively infrequent noise compared to engine speed.
I've checked the really obvious - signs of any vibrating pipes catching when they shouldn't be, exhaust manifold cover plate not loose, coolant / oil OK etc. Cam belt is still well within the expected lifetime (but I'm not sure if things like water pump etc. have ever been done)
Any theories? I'm reluctant to do any serious tearing apart of the engine, but it'd be nice to get to the bottom of what's causing it (and whether it's something serious/terminal or not! :-)
cheers
Jules