[TwiceHorn]

I reported this some time ago, but it may have gotten a little worse.

When I stop the engine on my 17 Coupe 2.0, there has often been a kind of "wheeze" noise that I rightly or wrongly associate with the ventilation/AC system depressurizing. It's not loud or anything, just noticeable. But, for the most part, it doesn't or didn't seem to happen on engine stop/start, only when I actually stop the engine and prior to exiting the car. It is what I would call a "pneumatic" noise and it comes from what seems like under the dash or the cowl area. It could even be a turbo-related noise, but I tend to think not.

Well, in this heat, the AC is working overtime and I am getting a few more noises from that general ares and now they show up during engine start/stop, but not when I stop the engine. It's not the pure wheeze anymore, but has some more "mechanical" noise to it, like gears operating a little and a door closing. I can also get it if I change the temperature more than 2-3 degrees at a time, as in to cool the cabin after sitting in the sun a while.

I kind of suspect that this has something to do with the blend door actuating and opening/closing. It doesn't sound bad, like "grindy" or anything, just I can hear the operation a little bit. I won't say most people, but a lot of people probably wouldn't notice at all. I'm mechanically sensitive, though.

Is this in any way related to the blend door failure that I have read about? My extended warranty ends in February '23 and I'd like to and will bring it to the dealer's attention as sort of a "warranty issue" at the next visit, which should be in a month or so.

Thanks for any insight.

 

[14BlueRocket]

It's hard for us to say what it might be without hearing it for ourselves. Any way you can record the sound with your phone, post the video to YouTube, and then link it here for us to listen to?

From your description, it does sound like something HVAC related. Has it always done this or is it more noticeable to you lately? It may or may not be a failing component, so if you are under warranty then a dealer visit is the right thing to do. The worst they can do is say "Can't find it".

Another thought: if your cabin air filter failed, or someone replaced it and let rubbish into your system, it could be the air flow changed due to a blockage. I have a vibratey noise from my system at the moment due to leaves falling in after I changed the filter last year. Been too lazy to pull the blower fan to clean it out since it involves removing the passenger-side knee airbag.

 

[TwiceHorn]

It's hard for us to say what it might be without hearing it for ourselves. Any way you can record the sound with your phone, post the video to YouTube, and then link it here for us to listen to?

From your description, it does sound like something HVAC related. Has it always done this or is it more noticeable to you lately? It may or may not be a failing component, so if you are under warranty then a dealer visit is the right thing to do. The worst they can do is say "Can't find it".

Another thought: if your cabin air filter failed, or someone replaced it and let rubbish into your system, it could be the air flow changed due to a blockage. I have a vibratey noise from my system at the moment due to leaves falling in after I changed the filter last year. Been too lazy to pull the blower fan to clean it out since it involves removing the passenger-side knee airbag.

The airflow is unchanged, as yet. It blows cold and strong out of all the dash vents.

It has made the wheeze since I bought it in January 2020. Hasn't gotten worse. It might actually be the turbo spinning down and things depressurizing.

The little grinding noises during start stop and temperature changes (they're not gritty grinds, they sound like gears operating) very clearly come from within the dash. It sounds like an actuator actuating, pretty normal from a mechanical standpoint, but it's not usually audible in cars. It's probably too faint to record without an actual microphone, radio at low volume covers it up.

I may have just noticed it because it's so friggin hot and I wind up bumping the temp down for a bit to cool the interior. Dunno about the stop/start thing. For one thing, it's unusual for the engine to stop when the ac is running, but not unheard of. Maybe when the engine stops, the ac reverts to some low state and when it and the compressor come back on it opens/closes the blend door.

I'm going to guess that because no one can relate to the noise I'm describing and lots of people have had the blend door failure problem, that it probably doesn't indicate anything. I will mention it to the dealer, though.

 

[angel71rs]

It has made the wheeze since I bought it in January 2020. Hasn't gotten worse. It might actually be the turbo spinning down and things depressurizing.

Possible it could be something like this?:

Wastegate solenoids

3 years and 20k miles ago, my car would make a hum when I turned the car off. The dealer confirmed it was the solenoids and replaced both under warranty. It solved the problem until recently. The hum has returned. I'm assuming its the solenoids again. I'm out of warranty and I would prefer...

www.cadillacforums.com

 

[TwiceHorn]

Possible it could be something like this?:

Wastegate solenoids

3 years and 20k miles ago, my car would make a hum when I turned the car off. The dealer confirmed it was the solenoids and replaced both under warranty. It solved the problem until recently. The hum has returned. I'm assuming its the solenoids again. I'm out of warranty and I would prefer...

www.cadillacforums.com

No, the "wheeze" is a kind of "spin down" noise, like a fan or turbo going from speed to stop, with an accompanying sort of pneumatic sound.

Maybe the better question to ask is if there is any kind of noise that typically accompanies blend door actuator failure?

 

[14BlueRocket]

How loud is the "spin down" noise? It could also be your transmission shifting to a lower gear if it occurs as you come to a stop. My dad's '77 Corvette makes a very distinct whirring sound as it shifts to 1st as I come to a stop in it. I have an AWD ATS and can hear the transfer case sometimes if the road surface is smooth enough. Very faintly, however.

For noises associated with blend door failure, I would expect it to sound like something stripped out or nothing at all. The only blend door failure I ever had was on my Buick Park Avenue, and it completed died.

Any chance you can record the sound for us?

 

[mariodave66]

Does it do it if the A/C is not on?

 

[Cadillac Customer Service]

I reported this some time ago, but it may have gotten a little worse.

When I stop the engine on my 17 Coupe 2.0, there has often been a kind of "wheeze" noise that I rightly or wrongly associate with the ventilation/AC system depressurizing. It's not loud or anything, just noticeable. But, for the most part, it doesn't or didn't seem to happen on engine stop/start, only when I actually stop the engine and prior to exiting the car. It is what I would call a "pneumatic" noise and it comes from what seems like under the dash or the cowl area. It could even be a turbo-related noise, but I tend to think not.

Well, in this heat, the AC is working overtime and I am getting a few more noises from that general ares and now they show up during engine start/stop, but not when I stop the engine. It's not the pure wheeze anymore, but has some more "mechanical" noise to it, like gears operating a little and a door closing. I can also get it if I change the temperature more than 2-3 degrees at a time, as in to cool the cabin after sitting in the sun a while.

I kind of suspect that this has something to do with the blend door actuating and opening/closing. It doesn't sound bad, like "grindy" or anything, just I can hear the operation a little bit. I won't say most people, but a lot of people probably wouldn't notice at all. I'm mechanically sensitive, though.

Is this in any way related to the blend door failure that I have read about? My extended warranty ends in February '23 and I'd like to and will bring it to the dealer's attention as sort of a "warranty issue" at the next visit, which should be in a month or so.

Thanks for any insight.

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[TwiceHorn]

Well, I took it in with the power steering failure and, sure enough, something in the blower motor was binding, so replaced.