Loud buzzing in oil filter area 2008 S60 2.5T "Astrid"

veektor · Post by **veektor** » 04 May 2019, 18:50

My wife and I have been driving Astrid around town, and it's been a good commuter car for us. We've decided that after over 2K miles on the 'new' engine (salvaged from '06 XC70) we had enough confidence in Astrid to take us to our Spring Vacation. Installed new front brakes and all four brand new tires.

Today I happened to look underneath while the engine was running, and heard a rather loud buzzing noise. I traced to see if it was the tensioner pulley, but the sound wasn't noticeable when looking down into engine bay. Sounded like a bad bearing on an idler wheel, but I could feel the buzzing on the oil filter cap.

Anyone have ideas what I am up against? Should I be prepping up my 10mm for removing the oil pan?

Post by **oragex** » 04 May 2019, 19:11

That could be the A/C compressor bearing. This is how to easily locate the noise - but be extra careful around rotating parts. May also pull the dipstick tube see if the noise stops

Post by **RickHaleParker** » 04 May 2019, 19:31

veektor wrote: ↑04 May 2019, 18:50 I traced to see if it was the tensioner pulley, but the sound wasn't noticeable when looking down into engine bay. Sounded like a bad bearing on an idler wheel, but I could feel the buzzing on the oil filter cap.

Did you take a stethoscope and play doctor?

Post by **jimmy57** » 04 May 2019, 22:15

The relief valve for the piston cooler jets is on the front of the engine below water pump. It looks like a 17mm bolt head screwed into engine. If that is the cause then the buzz will stop if you raise engine speed. The oil pump volume will go up and the valve will quit cyclically opening, dropping oil pressure, closing, oil pressure goes up, etc etc.

veektor · Post by **veektor** » 07 May 2019, 13:06

I am ashamed to report that I still have not raised the car to inspect this noise up close, too many things on my plate.

That first evening when I noticed the noise, I told my wife "we may have a problem", and went outside to show her. Started the car, but only the tensioner pulley was making noise, nothing from the bottom. I was starting to think that my youthful indiscretions with psychedelics were coming back to haunt me as flashbacks. Next day I started her up again, popped the hood, and stood in the front to listen. Shortly after the initial high-rev died down, I heard the noise from the bottom again. Jimmy57 may be on to something, because other than a noisy bearing, the noise could be attributed to a jet of aerated liquid, or sometimes escaping bubbles make a similar buzz. I will have a helper today who will rev the engine for me while I listen to validate the correlation of buzzing and low engine speed.

If Jimmy is right about the cause of this buzzing, is this something that will eventually lead to some damage, or just another 'quirk'? I am still new to this engine family, and especially paranoid because this was a junkyard sourced engine, without any known history.