astra 16v , grinding noise when you start the engine !!! ?

we have a n reg 1.6 16v astra and its making a making a knocking / grinding noise when you start the engine !!! its coming from the side where the battery is ? it only does this when the engine is cooled right down . once you have been driving for about a minuite it stops and wont make the nosie untill the car has been left for over 2 hours to cool . can someone help as there seems to be nothing over that side of the engine, just the battery ? pls help

Reply to
flipside
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I think you will find there is an air pump over there, it reduces start up emission levels IIRC

Reply to
MrCheerful

This is the secondary air pump, it should sound like a vacuum cleaner and runs for upto 30seconds, only at cold start. Yours probably is on its last legs, and when it dies (seizes up) the check engine light will come on. You'll need it fixed for your next MOT.

Tim..

Reply to
Tim..

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