Odd noise at 1-2 psi under load....

[josemateos]

I'm getting an odd noise, it sounds like someone blowing over a glass bottle....I might also compare it to a whale noise or a wheel bearing going out (its not wheel bearing). It's been getting worse over the last 4 wks. I just figured out when it happens....IT HAPPENS WHEN MY TURBO NEEDLE IS IN BETWEEN WHITE AND YELLOW. So basically when the turbo kicks in, as white is all crankcase pressure I believe. Anyhow, if I'm going up a hill it's much more noticeable, but I'm not sure if it is because of the load, I think it is more due to the fact that the needle is more likely to be and stay in that position, if I keep the throttle so the needle stays at that exact pt the noise will continue and continue on. I noticed a similar thread here http://answers.yahoo.com/question/in...6103918AATvp0g

He explains it the same way, the sound air over an empty bottle, although he says when the turbo is fully engaged. I did replace my vacuum lines recently, I also did the T7 Faster response update from SaabTuners.com, which I mentioned in another post. Anyhow, now that I see it is happening at that exact pt I'm leaning toward turbo issues. Before I thought it might have been a throwout bearing or something to do with the clutch, at this pt I'm certain it's turbo related just not sure what. Turbo sounds great past that, I have open air intake so BOV is loud and I've tested it already by applying vacuum and it holds just fine. Any help would be appreciated

Has this ever happened to anyone? If so what was it?

[rpiereck]

Your turbocharger bypass valve is the culprit. As it gets old it starts hooting, as when it switches from atmospheric pressure to boost pressure the internal parts vibrate.




The valve is very easy to replace and a stock one shouldn't cost more than $40 new, but I heard sometimes the noise does not go away.

A Forge valve is more expensive but will make the noise go away as it is built slightly different inside. The Forge valve is $140 from Genuine Saab, but good copies can be had on eBay for $30-50. Search on eBay for Bosch turbo valve, as it is a standard Bosch part used on many different turbocharger systems (Saab, Porsche, BMW, etc).


You can however try to flip your valve around, the operation of the turbocharger system is not affected if the valve is installed backwards, so you might try and flip the valve 90 degrees where it is mounted. A backwards valve might give off a sneezing sound instead of a hooting sound, or it might not make any sound at all. Worth a try.

[josemateos]

Appreciate your response, I will try flipping it around and see if it helps. The only reason I had discarded the BOV as the culprit is because I tested it a couple weeks ago. I just hooked the mity vac to the small hole pull a vacuum and checked to make sure it held and it did.....maybe I should check it again. I will do that this weekend, and update the thread. Thx for your help!!

[josemateos]

I've been told on saabcentral that this sound is most likely my exhaust manifold bolts. I was told the engine mounts loosen causing bolts to shear....I will be checking both soon to see if I can figure this out

[Burnsside42]

Don't flip your Boost diverter valve around please - not advised. It only fits one way for reason. It only works one direction.

Can you somehow take video clip of the noise? If you could and post it that would help a lot.

[josemateos]

I can try & video the noise but it is hard to hear above all other noises ....I tried out once....I will try it again. I saw most the bolts from the exhaust last night and they looked okay, didn't get into it but I looked real quick with a light. I did a check on my diverter valve by hooking my MityVac to the vacuum line and pulling suction.....it held steady @ 16 psi for several seconds.....I didn't check for long periods but I wasn't sure that I needed to.

*Is that a good test for a diverter valve?
*Is there another test I can do?

I will check on the video to see of I can give u a better idea, I can say it really does sound exactly like blowing over a glass bottle and happens right when turbo stays to kick in (middle of white & yellow on turbo gauge)

[josemateos]

Oh yes I tried switching the valve... it wouldn't fit....would've had to cut some of the metal pipe back....not a good idea:sly:

[josemateos]

Here's a video of the noise....see when it switches from atmospheric pressure to turbo...it's the noise you're hearing in the background....it's basically constant once it starts since I'm driving up a hill I was able to keep it going.....sounds like blowing over glass bottle as I said before.....check the video here. http://db.tt/ZnCrP8Vv

Let me know if that doesn't work, I saved it to dropbox and put in the link? Thx

[josemateos]

Bump.....nobody recognizes the sound? Thx

[josemateos]

I think I found my answer here on Saabworld at this link: http://saabworld.net/f9/odd-noise-1-...er-load-28956/

Not 100% sure it's BOV though, still thinking a small leak somewhere in turbo system....