I have got a Octavia 2003 2.0 petrol engine and it started yesterday to make a strange and extremly loud fan noise but when a shut the car down and started it again it was gone, but now when ever i start the car and it has been stopped for more then a half an hour it starts again when i restart the car. do u know what could be wrong, i am very nervious to drive the car

Is the fan belt screeching in which case it needs tightening or is the noise actually coming from the fan when car engine very hot?

Agreed.

Also, I have a home ventilation fan which sometimes makes a screeching noise because it's slightly off-line in its duct, and the blades rub. This should be easily diagnosed by the rough feathered edges on the blades.

Well the sound is not coming from the fan itself and it is louder then a aircompressor and when i restart the car it is gone

Have you got a fault code reader you can check for any codes with?

Might be secondary air injection pump (do a search on here) but I'm not sure if those are fitted on the 2 litre petrol engines.

Here is a video http://s18.photobucket.com/albums/b113/hjalti/?action=view&current=MOV04063.flv

And there are no fault codes

No one?

[if the noise seems like it is coming from the passenger side, inside the car then it could be the motor which controls the direction of air flow. I had a noise like this on mine, if you mess about with the air con (presuming its an elegance) the noise changes pitch and regularity. I was concerned so i took it to my mechanic who said it would not affect the running of the car and would be expensive to fix so I could just put up with noise. needless to say, I christened the sound 'neil the noise' and just put up with it for three years. Some times I wouldnt hear from neil for weeks but the it would only take the door to shut too hard and he would be back!

If it is the same problem, get it fixed if you want to but dont worry about it.

There's another fan inside the aircon unit too. There are a couple of buttons on the Climatronic control panel that change the ventilation fan speed, maybe try setting it up and down and see if you can change the note to confirm/deny this as the cause?

Edited 17 May, 201016 yr by KenONeill

Found out what it was, the hose from the secondery airpump was leaking