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Intermittent low knocking from engine bay, heard when hot and at idle - s70 NA Manual Topic is solved

Help, Advice and DIY Tutorials on Volvo's extremely popular car line -- Volvo's 1990s "bread and butter" cars -- powered by the ubiquitous and durable Volvo inline 5-cylinder engine.

1992 - 1997 850, 850 R, 850 T5-R, 850 T5, 850 GLT
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1997 - 2000 V70, V70 AWD
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abscate
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Re: Intermittent low knocking from engine bay, heard when hot and at idle - s70 NA Manual

Post by abscate » Tue Oct 01, 2019 3:50 am

I completely forgot about the freewheeling pulley

That came on in the 1999 models and the SERP belt route changes ( the alternator spins backwards relative to the rest of the cars this Forum)

I have the splinedtool to remove the pulley, that sucker is on really tight and is a left hand thread.

The hose method would point this. If you remove the SERP belt you can also feel the alt pulley and tensioner for play.
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Re: Intermittent low knocking from engine bay, heard when hot and at idle - s70 NA Manual

Post by theWIFES_S70 » Wed Oct 09, 2019 11:04 pm

Image

Sounds like this is loose... I'd make sure this piece is tightened down enough. Pretty easy to get a wrench on it. I had a similar sound 6 years ago.
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Re: Intermittent low knocking from engine bay, heard when hot and at idle - s70 NA Manual

Post by smacknab » Sun Oct 20, 2019 8:25 am

Just to update this. The noise got really really loud and no longer intermittent. My car ended up having a no-start issue which I eventually found out was caused by a seized ac compressor. So, not sure which came first, since the mechanics did seem adamant that there was play in the alternator pulley, but maybe that was damaged by a improperly working ac compressor.
99 s70 NA m56 - >217k miles

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Re: Intermittent low knocking from engine bay, heard when hot and at idle - s70 NA Manual

Post by abscate » Sun Oct 20, 2019 1:54 pm

Could be, but more than likely they missed it. It happens

Eventually you will find out your next timing belt on your 1999 isn’t due until 310,000 miles, but I’ll keep that secret for now
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Re: Intermittent low knocking from engine bay, heard when hot and at idle - s70 NA Manual

Post by smacknab » Sun May 03, 2020 6:27 am

Just to follow up on this it was my AC compressor pulley bearing. I finally tore the old one apart and it was rusted out with all the bearings bunched up
99 s70 NA m56 - >217k miles

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