longy44

Member

• May 25, 2016

• #1

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.

 

hd3

Well-Known Member

Full Member

• May 25, 2016

• #2

does it have air con. ?

 

longy44

Member

• May 25, 2016

• #3

yes it does have aircon,i did not turn that on though when it made this noise.

 

hd3

Well-Known Member

Full Member

• May 25, 2016

• #4

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

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

 

freelance

Well-Known Member

• May 25, 2016

• #5

Most likely the crankshaft pulley needs replacing, the damper gradually gives up,

 

Nodge68

Well-Known Member

• May 25, 2016

• #6

freelance said:

Most likely the crankshaft pulley needs replacing, the damper gradually gives up,

Click to expand...

+1

 

longy44

Member

• May 26, 2016

• #7

freelance said:

Most likely the crankshaft pulley needs replacing, the damper gradually gives up,

Click to expand...

jf it was the crankshaft pulley you would have noise all the time,this only makes a noise when demist operated.

 

Nodge68

Well-Known Member

• May 26, 2016

• #8

longy44 said:

jf it was the crankshaft pulley you would have noise all the time,this only makes a noise when demist operated.

Click to expand...

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.

 

GrumpyGel

Well-Known Member

• May 26, 2016

• #9

Shine a torch at the pulley and see if there's any sparkling dust around it.

These pulleys have been known to make noises under varying conditions when they start to fail.

 

longy44

Member

• May 26, 2016

• #10

ok will have a good look round pulleys and air-con pump see if i can see anything,will have to be tomorrow now.