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159SW, 1.9 16v 110KW diesel
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Discussion Starter · #1 ·
Hi,

I have experienced a strange noise. It only appears when engine is running at about 1500-1900 rpm and even then its not always there, comes and goes. It kinda fades in and fades out. When this noise is annoying me, i step on the gas, car downshifts, rpm goes higher and the noise is gone. When it then shifts back to the appropriate gear, the noise doesn't come back momentarily, but rather at a seemingly random time.

The sound is like someone is cutting wood on a miter type saw half a km away. Not metal on metal grinding, but rather vibrating(?) noise?? I could be wrong.

The noise isn't loud, when music is playing on volume 6-7 (stock radio) i can barely hear it.

It doesn't cause anything negative to the performance as far as I know.

Anyone know what could be the cause of this and tell me if it could break or wear something out in the long run?
Thanks in advance.

159 SW, 2007
1.9 jtdm, automatic transmission
driven 190000km
 

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Where is noise coming from?
My 159 did similar a sort of grinding behind the dash,common issue when air con gas is low. Try switching air con off see if it changes
 

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I have a rattle in the back at 1500rpm, fuel line vibrating below the rear seats. Still have tot take them out to check whats going on, but if I tape the fuel line that comes from the tank below the car, the noise is gone for about 10km.
 

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Mine does that aircon full or empty! Been told it is a dodgy belt tensioner, but does seem to be affected by how hard the ac is working
Turn your ac off, see if that affects it.


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Can’t see it’s a tensioner as that will be noisy all the time, most likely a weak compressor or the expansion valve causing it I reckon. Does the noise sound like behind the dash?
 

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159SW, 1.9 16v 110KW diesel
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Discussion Starter · #6 ·
Hi, thanks for your replies

I now am pretty sure that the AC is making this noise. When I switch AC off, the sound is gone withing a second, and when turned back on, it comes back. Tried it about 10 times, performed that way every time.

So this indicates low AC gas level or some other problem? Which parts of an AC are actually connected to the engine crankshaft? Some connection should be, as the pitch changes in correlation with RPM.

Thanks again
 

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Just the compressor connected to crank.
The noise I suspect is caused by slightly low pressure in system causing air type noise through the TXV. A regas should sort it,certainly did with mine.
I just treated the noise as an early indication I had a slow leak,was fine after regas but several months later it started again. Turned out my condenser was on its way out so changed that and gassed again.
 
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