I have owned a 52 reg Astra mk 4 SRI turbo -standard Z20 let no mods - since last Feb. Mileage at present is 31500. 2 weeks after buying the car there was a loud "whiring" noise from the engine. Took it to local Vauxhall garage and they told me cam pulleys and water pump were on their last legs so they were replaced. Shortly afterwards, a "knocking/rattling" noise became audible - especially when the engine is cold and the car is being driven and it is easier to hear with the windows open on a road where the are buildings around for the noise to bounce back off - dealer at first denied it was there . It seems at it's worst when the revs are around 1500/2500 and when the engine becomes warm, the noise dies down although is still there. Also when stationary, a blip of the throttle will result in a bit of a rattle initially but nothing afterwards - making it hard to determine where exactly the nopise comes from. Been back to Vauxhall who have again changed the waterpump followed - after a long wait for parts- by the camshafts/lifters etc. Even after this work, the engine sounds exactly the same and while doesn't appear to be getting any worse it is not getting any better and the warranty on the car runs out end of October 05. The local dealer have apparently had a Vauxhall engineer to see the car but no one seems to know what the problem is let alone a way of repairing it!! I was told it does not warrant a new engine yet!! - but was wondering if anyone else had experienced similar noises/problems and if so what the fix is/was? If you turn up the CD and close the windows it cannot be heard but there must be a better solution than that?? I think the noise is coming from the bottom end of the engine -crankshaft/piston? - but that is just a guess....The car is not losing oil/water etc and there appears to be no loss in performance - so nothing obvious springs to mind.
Any help appreciated.