nasty metalic rattle

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longy44

Member
Posts
13
Location
alford lincolnshire
hi guys,stood on the drive today with engine running fiddling with the heating knobs and i turned the heating fan on then turned first knob to demist and got a really nasty metallic grinding noise,has any of you got any idea what would cause this.i have listened under bonnet and it appears to come from belt area on engine,but it only does it when demist is selected.any help gratefully excepted.
 
air con is 'on' when demist or demist+footwell is selected
( there's a microswitch on the air-route selection dial )
regardless of the AC dash switch position

so 'noise' will have something to do with the aux. belts pulley system
and / or the ac compressor
the crankshaft one is known to come apart with age .. and makes 'orrible noises
then there's a belt tensioner that gets mentioned as a noise source

someone else with detailed knowledge of the belt-pulley system might give more info

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jf it was the crankshaft pulley you would have noise all the time,this only makes a noise when demist operated.
It's making the noise on demist because of the added load imposed by the AC pump. I suppose it could be the AC pump itself causing the the noise, but the pulley is a known failure item.
 
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