Air pump questions

[boltoa]

First off, what exactly does it do?

Secondly, I was having my clutch replaced last week, and the mechanic said that when he was running the engine up up on the lift, it was making a funny buzzing noise as the revs rose. I looked myself as I can\'t hear it in the car, and sure enough, with me opening the throttle from under the bonnet, at about 3000ish revs (can\'t be sure of this), the air pump pulley made a funny noise and the air pump inner pulley stopped rotating. I suspect it has some kind of electromagnetic clutch like an air con compressor, but I was wondering if this was normal? It seemed fairly consistent, so I suspect it is designed this way, but I just wondered why?

Thanks for any info.

Andrew

[bnaellis]

Hi Andrew,

Yes it\'s normal the airpump cuts out at approx 2500rpm
the funny noise you here would be if you have a aftermarket induction this is normal too.

rgds

[boltoa]

Thanks for that.

You misunderstand me slightly - it\'s the air pump pulley magnetic clutch that makes the buzzing noise as it disengages. Looks like it has some kind of braking mechanism to stop it rotating fairly quickly after the clutch disengages.

So what is the purpose of the air pump anyway?

Andrew

[bnaellis]

The airpump pumps air into the cat to lower the harmful emission polluting the atmosphere.

rgds