Source of screeching noise?

hajjat · Post by **hajjat** » 15 Aug 2021, 23:09

Hi Volvo'ers!

I started getting an annoying screeching sound when engine is at 1.5-2 RPM (whether it's idle or driving). My car is 04 Volvo XC70 with 173k miles. Car doesn't make noise at lower or higher RPMs.

I recorded the sound here:

I tried:
- Opening up oil cap and dip stick, but screeching is still present
- I replaced the serpentine belt today to no avail. Car still makes screeching noise.
- Moved pulleys manually by hand (shown in video) to try to recreate the noise but couldn’t. I noticed all pulleys move fine except the lower inner one (crank shaft?); is that normal?
- Turning the steering wheel doesn’t trigger the noise (thought could be the steering pump)

Could it be one of the pulleys? If so, any idea how to isolate the sound and identify the root cause? Anyone had a similar issue?

Any help is greatly appreciated! Thanks a lot!

Post by **MoVolvos** » 16 Aug 2021, 04:54

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Surgically squirt a little WD into the suspect bearing and see if the noise goes away. Water can also be use for testing if you think the oil will make too much of a mess.

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Post by **abscate** » 16 Aug 2021, 05:06

You can use a hose as a stethoscope to track down the noise source. Did it still make the noise with the serpentine belt off?

Post by **Blacklab467** » 16 Aug 2021, 17:32

It sounds to me like an alternator bearing, but that's just my best guess. How long has it been doing it? If it is a bearing it will manifest itself in fairly short order.

Post by **br0dy519** » 16 Aug 2021, 20:26

Almost the same tone and pattern as a bad blower motor

You can always remove the alternator and bench it at an alternator/battery shop.. if it's the alt pulley it will sound like a screaming pig, that's what mine sounded like on the bench!

hajjat · Post by **hajjat** » 17 Aug 2021, 00:01

Update: RESOLVED!! It was the tensioner pulley!

Thanks for the suggestions! Here's is what I did:
* Bought a 3/8" OD clear vinyl tube from HomeDepot to use it as a stethoscope to track down the noise source. Boy! I was so impressed by this! I was able to locate other minute problems. I spent the day listening to every part of the engine

Thanks @abscate!
* Squirted a little WD-40 into the pulleys one by one and turning on the engine every time. The moment I did it on the tensioner pulley the sound went away, voila! Just like that!!

Thanks @MoVolvos!

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Other notes:
* @Blacklab467: Thanks for the suggestion. I was afraid it was the alternator, but luckily I didn't have any of its symptoms. I don't have to buy a new one, pheow!
* @br0dy519: Great suggestion! Luckily it got resolved before I had to do this. Great tip tho, will use it if alternator fails in future!

Post by **abscate** » 17 Aug 2021, 01:46

I spent the day listening to every part of the engine Thanks @abscate!

I do this at 0300 until the cops come. If you do it during the day, the white truck with the guys with the big butterfly nets come and try to take you away.

Post by **MoVolvos** » 17 Aug 2021, 08:06

hajjat wrote: ↑17 Aug 2021, 00:01 Update: RESOLVED!! It was the tensioner pulley!

Thanks for the suggestions! Here's is what I did:
* Bought a 3/8" OD clear vinyl tube from HomeDepot to use it as a stethoscope to track down the noise source. Boy! I was so impressed by this! I was able to locate other minute problems. I spent the day listening to every part of the engine Thanks @abscate!
* Squirted a little WD-40 into the pulleys one by one and turning on the engine every time. The moment I did it on the tensioner pulley the sound went away, voila! Just like that!! Thanks @MoVolvos!

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Other notes:
* @Blacklab467: Thanks for the suggestion. I was afraid it was the alternator, but luckily I didn't have any of its symptoms. I don't have to buy a new one, pheow!
* @br0dy519: Great suggestion! Luckily it got resolved before I had to do this. Great tip tho, will use it if alternator fails in future!

Nice work, glad you found the problem.

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