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

Post by **abscate** » 01 Oct 2019, 03:50

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.

Post by **theWIFES_S70** » 09 Oct 2019, 23:04

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.

Post by **smacknab** » 20 Oct 2019, 08:25

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.

Post by **abscate** » 20 Oct 2019, 13:54

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

Post by **smacknab** » 03 May 2020, 06:27

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