[Silver SAAB]

Anyone care to guess where this repeated clinking and clunking noise is coming from? Happens intermittently and is somehow related to the AC. If I turn off the AC it stops. I've checked the compressor, the lines and everything looks fine. It sounds the loudest on the backside of the engine where the turbo is. It sounds like something metal on metal that's closing and opening. It's not coming from behind the firewall, by chance I happened to put my ear on the air box and the intake hose and heard it resonate from somewhere deep inside the engine.


Loaded a video to YouTube:

 

[aerojon]

that doesn't sound healthy,i'd be checking the turbo for excess play in the shaft..

 

[Silver SAAB]

I did take off the intake hose and put my finger on the shaft. There's no play in it at all, spins like it's supposed to. The only clue I have is that the noise stops when the AC is turned off. Not sure how or why that's related, but it is. It happens intermittently when the engine is first started, at least that's the only time I've heard it. I'll be replacing my water pump soon so I should be able to get a better look behind the engine.

 

[steve12955]

If you suspect it's the AC compressor or pulley-related, shoot another video on the other side of the engine and move the camera as close as you can to different spots on that side.

Idler and tensioner pulleys can make strange sounds when they're on their way out but your sound is definitely more of a knock. Was the AC system recently charged? Sometimes, an over-charged system can cause the compressor to make a knocking sound.

 

[Silver SAAB]

I finished replacing the water pump and while I had all the parts off the car I looked around for what that noise could be coming from and the only thing that has moving parts on the backside of the engine that are metal on metal is the turbo wastegate. I took a picture of what could possibly be making the noise. I haven't heard it since I made the video and hope it's gone away for good, but I think whatever this flap is inside the wastegate is what made the noise.

 

[Diggs]

That's....the wastegate.

 

[Silver SAAB]

What causes it to open and close? I'm guessing that's what was making the noise in the video I made. I filmed it just after I started the car and it was idling.

 

[mcgyvah]

Are you sure its not just the heatshield rattling?

 

[Diggs]

 

[Silver SAAB]

Mcgyvah: No, I'm not sure. If you listen to the clinking and clunking noise in my video it sounds like it's coming from something made of metal that's thicker and heavier than the thin aluminum heatshield. It could even be the metal on the cat expanding and contracting, for all I know. Thankfully, it hasn't happend since I made the video and the only other time I heard it was when I had an ignition coil go out on me a couple months ago that caused a misfire in cylindar 3. Fuel was getting into the cat and the engine light came on and I popped the hood to see what was the matter when I heard it coming from behind the engine. Anyway, everything's working properly now. I was just trying to figure out what the noise could have possibly been so I could double check to see everything's a-okay.

Diggs: Thanks for the informative wastegate video. If the noise ever comes back, I'll be sure to watch for the metal rod that connects the wastegate to the EGR to see if it's moving back and forth while the clinking and clunking noise is happening. I'll also make another video and try to get closer to where the sound is coming from.

Thank you both for your input.

 

[Silver SAAB]

I heard the strange tapping/knocking noise again this morning and had a quick second to record it. I still have no idea what is or where it's coming from other than the turbo area. It's definitely not the metal rod that connects the EGR to the wastegate.

Is there anything in the firewall behind the turbo that's AC related that could be making that noise? I didn't have time to turn the AC off this go round to see if the noise would go away. The last time this happened months ago I noticed when I turned off the AC the noise would stop.

 

[Silver SAAB]

Update: I heard it again today. This time I was able to turn off the AC and it stopped. Then I turned the AC back on and the tapping/knocking came right back. So the noise is definitely related to the AC somehow. The engine compartment was too hot to feel around or take off the turbo heat shield, so I wasn't able to narrow anything down. It's hard to tell with engine running but it sounds like it's coming from the turbo vacuum box or somewhere right near there. Just not sure how it's possible turning the AC on and off could affect that part. They're not related.