S80 Mysterious Whirring Noise Solved

Crito »

I thought this whirring noise I had was some sort of harmonic that inline sixes produce, since others have mentioned it in the forums too. But then I noticed that people where saying it happened at different RPMs than mine, and you’d think a natural harmonic would be produced at the same oscillation/frequency. So I started poking around and discovered that there’s a pipe that goes from a heat shield over the exhaust manifold (near where O2 sensors go) that runs into the air box — and now I also know why my Volvo warms up so fast in the winter. Well, in one place it was touching the block. So I tied it down with steel wire to the lower radiator hose, being careful to wrap wire around metal part and not rubber. Took it for a test drive, whirring noise is finally gone!

I can’t believe the problem was so stupid and the fix so simple. I’m attaching pics for reference.

Crito »

Well, got 90% of the whirring anyways. Still a little ~1850-1900 RPM, but was like from 1800-2500 RPMs before, so I’m pretty sure that corrugated aluminum tube is the source. I’m gonna try a couple hose clamps tomorrow to dampen the vibrations some more and hopefully that’ll make the fix 100% effective.

And if that doesn’t work I might just remove the tube entirely. So my car warms up a little slow in the winter… I don’t care, that noise was really bothering me — sounds serious (like bearings or gears or something like that) even though it really isn’t.

S80 Harmonic Noises and Rubbing Tubes

Well, I still have the 1850-1900 whir but it’s so slight I can barely hear it now. In fact, if rest of car wasn’t so quiet I probably wouldn’t hear it all all. So I’m keep the “Volvo engine noise amplifier” (my new name for it) out of the car permanently.

One last pic that’s a little troubling. Seems that tube had been rubbing against the lower radiator hose and ate a bald spot in it. I estimate about 25% of the hose material is missing in one section. The tube also seems to have shifted positions, so I imagine if it had stayed in the same place it may very well have eaten through 50% or more of the hose and caused it to fail.