Loud buzzing noise near Alt / Fuel Pump: not tied to RPM

orbital1 · Post by **orbital1** » 05 Sep 2020, 14:26

1998 V70XC w/165K on it. Runs great, but a new issue popped up I haven't come across before.
There is a really loud *buzzing* noise coming from the vicinity of the Alternator and Power Steering Pump. It is not tied to RPM - stays consistent whether idling or driving. Attaching an .mp3 link below.

I street park it in Brooklyn and have found rat droppings on the top of the engine just prior to the time this started. Took care of it by zip tying prescription bottles filled with peppermint oil-soaked cotton balls around the bay (works great BTW if anyone else experiences this). Nonetheless, the buzzing started after not long after finding the droppings sprinkled on the block. I've done a pretty thorough check of wiring and don't see any that's been stripped and haven't thrown any codes from a vacuum leak. It's nowhere near the fuel relay, so I've crossed that off. The only thing that seems to affect it is if I roll the windows up / create an electrical load.

I'm stumped. If anyone can help suss out what the cause is, I'd be greatly appreciative and can wrench on it myself. Otherwise it's off the my local indy for a wallet lightening.

Any ideas or similar experiences? Thanks!

Mark
https://www.mboxdrive.com/EngineBay_buzz.mp3

Post by **abscate** » 05 Sep 2020, 16:27

Start listening with a hose to isolate the noise. It could be one of the engine relays that hide under the cooling near that area

It could even be a vacuum leak in that area.

If there is too much gunfire to hear, wait for a clip change

bronco · Post by **bronco** » 05 Sep 2020, 17:26

no theory either way but next time I curl up on a warm engine if I get a whiff of pep-o-mint i'm gonna am-scray

orbital1 · Post by **orbital1** » 05 Sep 2020, 21:41

abscate wrote: ↑05 Sep 2020, 16:27 Start listening with a hose to isolate the noise. It could be one of the engine relays that hide under the cooling near that area

It could even be a vacuum leak in that area.

If there is too much gunfire to hear, wait for a clip change

Thanks for the heads-up on the relays nearby. Will scope it out. My XC throws a code if you even look at a vacuum hose wrong and it's clear, so I'm leaning towards a relay. Will post what I find. The only gunfire / backfire crack in my neck of the woods comes from fart-can equipped STI's.

Post by **ZionXIX** » 05 Sep 2020, 22:17

I assume the xc70s don't have those headlight wipers?

Multiskilled · Post by **Multiskilled** » 06 Sep 2020, 04:17

I had to disconnect my headlight wipers and also headlight hight motor adjuster

orbital1 · Post by **orbital1** » 06 Sep 2020, 13:38

ZionXIX wrote: ↑05 Sep 2020, 22:17 I assume the xc70s don't have those headlight wipers?

It does, but I took the headlight wipers off a few years ago. Didn't think to disconnect the relay for them.