'98 V70 Stick, Non-Turbo, FWD -Mystery sound like turbo spooling up @ between 2K & 3K RPM

[E Showell]

Car is a base model '98 V70 with 5 spd. manual trans and fwd., non-turbo.

Recent work -- 1) complete ignition tune up (Volvo plugs, Bosch Cap & Rotor, Bougicord wires); 2) Timing belt, water pump & serpentine belt replacement -- (Contitech belts, Aisin water pump, INA pulleys & brand name (can't recall which one) tensioner); 3) Front and Rear O2 sensors changed (Bosch for both); 4) replaced accelerator cable and engine air cleaner; 5) oil change.

On the drive home from Thanksgiving visit to in laws in Western NY, I got a CEL with Codes P0133 and P0140- if you check back through my post history, these codes seem to reappear annually about this time over the past couple years. Those are both O2 sensor codes, although many recount that they can be produced by a vacuum leak.

Since replacing the O2 sensors (yesterday) the CEL was extinguished and hasn't reappeared, although I suppose I have to put a few hundred miles on the car to be certain the codes are gone. While the codes were present this past weekend, the car started missing intermittently under load on a local state highway at around 50 mph (before all the recent work). That miss seemed to go away on its own. The car is running flawlessly now (I suppose I just cursed myself).

Here's the subject of the post -- around the same time I started getting the codes, I also began hearing what literally sounds like a turbocharger spooling up when accelerating in lower gears -- 1st, 2nd, between 2 to 3 K rpm. Now unless someone secretly installed a turbo in my car while I wasn't looking, it can't be a turbo spooling up. My mechanic heard it (on a very brief test ride when the car was having some other work [T-belt] done (I still don't trust myself to do a T-Belt change since the consequences of failure are too high a cost for me to bear right now), but said he didn't know what it was. I have looked around under the hood for a vacuum leak, but haven't been spraying starting fluid around in the engine bay. I have had the car for more than 7 years and never heard this sound. The car seems to be running well and it would not appear that the whine is affecting performance. The whine was present before all the recent work and did not go away as a result of the recent work.

Any thoughts as to what this could be? I'm stumped.

[scot850]

Hi Evan,

Can you record the noise and post?

Can you replicate the noise with the car standing, in neutral at the rev-range you mention?

Are you able to identify a rough area of the engine bay where the noise is coming from?

As a best guess if it only started after the new parts were fitted, then chances are it is something in the areas where the repairs/servicing was carried out. I'd be looking at one of the bearings in the serpentine belt area or the T-belt pulleys. Another possibility was I had a shreeking from my pulley system when coolant got on the serpentine belt, so maybe the belt or pulley is contaminated?

Neil.

[E Showell]

Neil -- The whine appears to be coming from the timing belt side of the engine, but it was present before any of the recent work was done. I could try to record, but it is very subtle -- if you were in the passenger seat, odds are you wouldn't even notice it if I didn't point it out.

[theWIFES_S70]

Possible whines from pieces that spin:
- Power steering pulley?
- Serpentine belt pulley?
- A/C Pulley?
- Timing belt roller?
- Timing belt tensioner?

I get a weird whine and "clunk-clunk-clunk" every so often, but it's from the driver's side of the engine. Near the air pump.

[E Showell]

Three of those are brand new.

[abscate]

What Neil said:

Have your lovely assistant spool up the revs while you listen with a hose in your ear.

That will tell you if its engine or driveline at very least

[theWIFES_S70]

What Neil said:

Have your lovely assistant spool up the revs while you listen with a hose in your ear.

That will tell you if its engine or driveline at very least

Yes, and make sure someone films you doing it so we can all see how it's done!

Good luck pinpointing the noise!

[abscate]

First time my neighbors saw this they locked up all the children

[E Showell]

Well. It is definitely engine-related. Revved up the engine in neutral at a stoplight and the whine was present.

[abscate]

That's good news. I was worried it was funky driveline something or transmission.

One of the idler pulleys, alternator whistle, maybe a resonant vacuum leak?