Whining or howling noise from engine

Yellowstone Savage · Post by **Yellowstone Savage** » 26 Apr 2012, 13:39

When my engine is warmed up to normal operating temperature I begin to hear a loud whine or howl coming from the intake area. The sound is present with the serpentine belt off so that rules out the alternator, power steering and AC. The noise does not change when the engine is revved in park, but changes tone or goes away when torque is applied (when accelerating while driving). It has a definite scrunch sound when the engine stops.
I recently replaced the alternator and radiator, and installed a complete tune up kit before the noise began. After the noise started I've replaced a leaking water pump, timing belt and tensioner. Now the service engine light just came on but I haven't pulled the code yet.

It doesn't sound this loud in real life, but please give it a listen and tell me what's up?

Post by **Ozark Lee** » 26 Apr 2012, 14:48

It sounds like the air pump for the SAS to me. It is a very expensive part but you can unplug it and then trick the ECU into thinking that everything is fine by soldering a diode across a couple of pins on the ECU connector. Details are here:

http://volvospeed.com/vs_forum/index.ph ... as-delete/

It does precious little for emissions since all it does is force air into the exhaust to heat up the O-2 sensor a tad quicker.

...Lee

Yellowstone Savage · Post by **Yellowstone Savage** » 26 Apr 2012, 22:25

Can I unplug the power to the air pump to see if the noise stops before I move on to the ECU trick?

eld4au6 · Post by **eld4au6** » 27 Apr 2012, 01:04

I'm not terribly knowledgeable but that 850 doesn't appear to have SAS.

Post by **erikv11** » 27 Apr 2012, 08:57

Yellowstone Savage wrote:Can I unplug the power to the air pump to see if the noise stops before I move on to the ECU trick?

Sure, good idea, but it will trip the Check Engine light and set a p0410 code. You just need access to a code reader to reset the code.

Post by **fields 100** » 27 Apr 2012, 13:03

Did not OP write that the noise starts when the engine reaches normal operating temperature ?
The SAS pump most of the time turns "on" only on the cold engine for approximately 120 sec.

Post by **erikv11** » 27 Apr 2012, 14:10

I agree, if the air pump is the problem then OP will want to figure out why it was on at all.

But if you listen to the video it really sounds like a howling air pump. Unhooking it is an easy way to test.

My next guess would be some kind of bizarre vacuum leak, but that is based on the video which may not reproduce the sound accurately.

Yellowstone Savage · Post by **Yellowstone Savage** » 27 Apr 2012, 14:54

Hmmm. I've been poking around in there and sure don't see the air pump. I even removed the hose from the air box to the throttle body to get a better look. I did NOT look up from underneath. What else could be howling?

BTW, the code I first mentioned was 170 related to a fuel mix issue, no doubt caused by a leaking vacuum hose on the fuel pressure valve. I taped the hose for now and the code cleared.

Post by **Ozark Lee** » 27 Apr 2012, 15:35

I should have looked more with my eyes than listened with my ears. You don't have SAS.

The only other motorized thing in the area is the Idle Air Control valve but I have never heard one sound like that. It is normal for them to buzz but not whine. The IAC valve is the silver cylindrical thing mounted just below throttle body. It has a hose from the airbox and another large elbow hose that runs to the vacuum tree. It is easily accessed if you remove the cover over the throttle linkage. You can try to unplug the electrical connector to the IAC and see if the noise goes away but the car will likely die after you unplug the valve.

...Lee

Oncloud59 · Post by **Oncloud59** » 27 Apr 2012, 21:09

Good day,
After reading and listening to the audio, one thing that might contribute to noises at idle can be a broken right side motor mount. It tends to make a rumble sound but could be higher pitched depending on what vibrates. The mount get exposed to oils and vibration and I have had to replace one on each of my turbo S70 and Xc 70. Each have over 100 thou. Jack the right side of the engine with a block of wood and see if it separates. Just something to look at..