NPP whistle
Thread Starter
8th Gear
Joined: Dec 2009
Posts: 8
Likes: 0
From: Renton WA
NPP exhaust whistle
I have a 2014 with automatic and NPP. In certain conditions, like pulling a hill, when the RPMs are just right, as the exhaust baffle is opening, there is a whistle sound. It goes away once the baffle opens (at least that is what I am assuming, not knowing exactly how this thing works). The dealer is telling me that's normal, that they all do that. I don't believe it.
I can't find any posts about this on the forum. If 'they all did that' I would think this forum would be lit up with complaints. Any suggestions on what to tell the dealer (polite ones please)?
I can't find any posts about this on the forum. If 'they all did that' I would think this forum would be lit up with complaints. Any suggestions on what to tell the dealer (polite ones please)?
Last edited by rmreeder; Aug 5, 2015 at 10:22 PM. Reason: More descriptive title
Drifting
Joined: Jun 2007
Posts: 1,425
Likes: 238
From: Macomb MI
Sounds like the "squeaky valve" syndrome. Sort of like a chirp. Both my NPP and AFM valves do this. Not normal, but not uncommon from others here.
If it bugs you, go back to the dealer and ask if GM designed them to squeak. If the answer is "No, but they all do that", well that's called a defect. If they won't repair, find a different dealer. The squeak is NOT from the actuators, it's from the valve assemblies.
If it bugs you, go back to the dealer and ask if GM designed them to squeak. If the answer is "No, but they all do that", well that's called a defect. If they won't repair, find a different dealer. The squeak is NOT from the actuators, it's from the valve assemblies.
Thread Starter
8th Gear
Joined: Dec 2009
Posts: 8
Likes: 0
From: Renton WA
Thanks --
Yup, crazybiker51, that's it. How did you fix it?
xp800, they are referring to a service bulletin which I believe describes something different. I took a tech for a ride and he heard it so we'll see what the story is. It's in the shop this week.
Rather than take it to another dealer, isn't there a way to appeal to a GM area service manager if this doesn't get resolved?
Yup, crazybiker51, that's it. How did you fix it?
xp800, they are referring to a service bulletin which I believe describes something different. I took a tech for a ride and he heard it so we'll see what the story is. It's in the shop this week.
Rather than take it to another dealer, isn't there a way to appeal to a GM area service manager if this doesn't get resolved?
Last edited by rmreeder; Aug 6, 2015 at 10:15 AM.
Supporting Vendor
Joined: Aug 2007
Posts: 1,451
Likes: 86
From: CT
pull the fuse out so the baffles just stay open all the time.. 
__________________
06MonteSS / DiabLew Tune
2014 Camaro 2SS/RS LS3, short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake, catch-can, ported/polished TB, Custom DiabLew Tune
www.diablewtune.com -- www.diablocustomtune.com -- www.diablocustomtunegm.com
06MonteSS / DiabLew Tune
2014 Camaro 2SS/RS LS3, short-throw shifter, NPP perf. exhaust, BMR strut-tower brace, Cold Air Inductions cold air intake, catch-can, ported/polished TB, Custom DiabLew Tune
www.diablewtune.com -- www.diablocustomtune.com -- www.diablocustomtunegm.com
Cruising
Joined: May 2016
Posts: 11
Likes: 0
C7 NPP whistle
Yes mine is doing it as well. In touring and eco mode more so. In sport mode less. Not at all in track mode - exhaust wide open. Just at tip in and then it seals up with a chirp at moderate throttle. 1550 miles on the car. Any idea what the repair is?
Thread Starter
8th Gear
Joined: Dec 2009
Posts: 8
Likes: 0
From: Renton WA
Exhause whistle
The dealer finally replaced the exhaust system. That cured the problem. They didn't have an answer when I asked if it was a design feature. They had been dragging their feet until then. I don't know if GM took care of it or if the dealer covered the cost for goodwill.
Cruising
Joined: May 2016
Posts: 11
Likes: 0
thanks - much appreciated
Many thanks . By the way I have had 2 other whistles. I changed a few things but what made the difference was the PCV valve, and the air inlet duct. They were not that much money so I changed them myself. As pointed out the car has 1550 miles on it. At delivery everything was quiet. These noises started at about 500 miles.
The exhaust is a different matter. I have yet to check whether the whistle is from the NPP exhaust valves or from a joint leak. I have looked at the valves and mufflers and there is nothing obvious. When I get time in the shop I will have a closer look.
If I cannot find anything obvious then I am thinking GM will have to replace the mufflers and NPP valves.
I will keep you posted - thanks again.
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