Bit of a clunk at startup occasionally??

CamaroRSOnt · 06-14-2020, 06:53 PM

Not sure what to make of it I get a kind of a clunk , almost like an actuator or something but just on occasion and only at startup. I wonder about the NPP exhaust opening or closing a valve? Funny thing is though it sounds like it is coming from the front end around the engine, believe the NPP valve is at rear.

It only happens about one in four or so on startup, before I put the tranny in gear or anything else, right after the engine starts. Never hear it again after that while driving and seems random on startup. I keep it in sports mode so that isn't changing. V6 with A10.

Anyone have an idea on what it might be? Car only has 800 miles on it. No point taking it in for this as it will be near impossible to duplicate as it kinda random. Thanks for any input.

Yellow Beast · 06-14-2020, 08:27 PM

Take it in if you really think its an issue. Leave it until they hear it. The car is new! We'd be guessing unless you post a video.

CamaroRSOnt · 06-21-2020, 02:04 PM

I did find this below related to all GM small trucks and passenger vehicles with automatics. Looks like they update this year to year because I found it updated 3 yrs in a row to include the current year vehicles.

Does sound a lot like it with the clunk issue but I don't get movement of the vehicle, it only happens after the vehicle has sat for the night as they describe in this below. I have also read that some have issues with a sticky solenoid that isn't quick enough to disengage with the flywheel at startup that can create a clunk sound as well. Will try their suggested parking brake fix from below.

Another forum member and I have swapped notes, seems we are having the same issue with our 2020's.

Holding off taking it in to the dealer until I get a better sense of where it is coming from and I can point them in the right direction. If you don't get the mechanics focused on the right thing dealerships can screw around and screw around with stuff like this wasting my time.

#08-07-30-026E: Information on Slight Vehicle Movement in Park at Start Up After Cold Soak - (Dec 12, 2017)
Subject: Information on Slight Vehicle Movement in Park at Start Up After Cold Soak

Models: 2018 and Prior GM Passenger Cars and Light Duty Trucks
Equipped with Automatic Transmission

Attention: This Bulletin also applies to any of the above vehicles that may be Export from North America vehicles.
This Bulletin has been revised to add the 2018 Model Year. Please discard Corporate Bulletin Number 08-07-30-026D.

2018 and Prior GM Passenger Cars and Light Duty Trucks
Equipped with Automatic Transmission

Some vehicles may rock or move slightly forward or rearward while in Park at start up after cold soak. This condition may be accompanied by a clunk noise. This is a slight movement that is more often seen visually, rather than felt, when viewed from the outside and using the auto-start feature, if equipped.

This slight movement is due to the residual transmission fluid in the clutch packs that creates a partial apply on start up. This movement is stopped by the parking pawl and/or transmission fluid exhausting completely from the clutch packs.

This condition is normal and no repairs should be attempted. This can be verified by comparing with another identically built vehicle under the same cold conditions.

Please communicate to the customer this condition is a normal operating characteristic of the vehicle. This slight movement has no adverse affects on the transmission. To prevent this condition from occurring, the parking brake should be utilized as per the Owner's Manual recommendations anytime the vehicle is parked. Please share this information with the customer including a copy of this message.

CamaroRSOnt · 06-21-2020, 02:27 PM

I see there was a thread on this same issue before, not uncommon the clunk at startup for quite a few of us. Seems like it isn't a big issue though so far as the performance of the car or tranny over time.

https://www.camaro6.com/forums/showt...ht=clunk+start

MRBLIV · 06-09-2023, 10:54 PM

This is the only thing I have found that is close to what I was experiencing. Right after start i hear a single clunk... Thing is brand new like I don't have my license plate new yet. Only happens on cold starts or right after a short drive. I have a video with a clear loud clunk. What was the fix or what was determined. Sorry just a bit paranoid haha.

2023 Camaro V6 A10

06-14-2020, 06:53 PM	#1
CamaroRSOnt Drives: 2023 SS Vert Join Date: Jan 2020 Location: Ontario Posts: 241	Bit of a clunk at startup occasionally?? Not sure what to make of it I get a kind of a clunk , almost like an actuator or something but just on occasion and only at startup. I wonder about the NPP exhaust opening or closing a valve? Funny thing is though it sounds like it is coming from the front end around the engine, believe the NPP valve is at rear. It only happens about one in four or so on startup, before I put the tranny in gear or anything else, right after the engine starts. Never hear it again after that while driving and seems random on startup. I keep it in sports mode so that isn't changing. V6 with A10. Anyone have an idea on what it might be? Car only has 800 miles on it. No point taking it in for this as it will be near impossible to duplicate as it kinda random. Thanks for any input. __________________ 1978 Z28 T-Roof 1984 Berlinetta 2007 Solstice Supercharged 2014 C7 Z51 2020 RS Convertible 2023 2SS Convertible

06-21-2020, 02:04 PM	#3
CamaroRSOnt Drives: 2023 SS Vert Join Date: Jan 2020 Location: Ontario Posts: 241	I did find this below related to all GM small trucks and passenger vehicles with automatics. Looks like they update this year to year because I found it updated 3 yrs in a row to include the current year vehicles. Does sound a lot like it with the clunk issue but I don't get movement of the vehicle, it only happens after the vehicle has sat for the night as they describe in this below. I have also read that some have issues with a sticky solenoid that isn't quick enough to disengage with the flywheel at startup that can create a clunk sound as well. Will try their suggested parking brake fix from below. Another forum member and I have swapped notes, seems we are having the same issue with our 2020's. Holding off taking it in to the dealer until I get a better sense of where it is coming from and I can point them in the right direction. If you don't get the mechanics focused on the right thing dealerships can screw around and screw around with stuff like this wasting my time. #08-07-30-026E: Information on Slight Vehicle Movement in Park at Start Up After Cold Soak - (Dec 12, 2017) Subject: Information on Slight Vehicle Movement in Park at Start Up After Cold Soak Models: 2018 and Prior GM Passenger Cars and Light Duty Trucks Equipped with Automatic Transmission Attention: This Bulletin also applies to any of the above vehicles that may be Export from North America vehicles. This Bulletin has been revised to add the 2018 Model Year. Please discard Corporate Bulletin Number 08-07-30-026D. 2018 and Prior GM Passenger Cars and Light Duty Trucks Equipped with Automatic Transmission Some vehicles may rock or move slightly forward or rearward while in Park at start up after cold soak. This condition may be accompanied by a clunk noise. This is a slight movement that is more often seen visually, rather than felt, when viewed from the outside and using the auto-start feature, if equipped. This slight movement is due to the residual transmission fluid in the clutch packs that creates a partial apply on start up. This movement is stopped by the parking pawl and/or transmission fluid exhausting completely from the clutch packs. This condition is normal and no repairs should be attempted. This can be verified by comparing with another identically built vehicle under the same cold conditions. Please communicate to the customer this condition is a normal operating characteristic of the vehicle. This slight movement has no adverse affects on the transmission. To prevent this condition from occurring, the parking brake should be utilized as per the Owner's Manual recommendations anytime the vehicle is parked. Please share this information with the customer including a copy of this message. __________________ 1978 Z28 T-Roof 1984 Berlinetta 2007 Solstice Supercharged 2014 C7 Z51 2020 RS Convertible 2023 2SS Convertible

06-21-2020, 02:27 PM	#4
CamaroRSOnt Drives: 2023 SS Vert Join Date: Jan 2020 Location: Ontario Posts: 241	I see there was a thread on this same issue before, not uncommon the clunk at startup for quite a few of us. Seems like it isn't a big issue though so far as the performance of the car or tranny over time. https://www.camaro6.com/forums/showt...ht=clunk+start __________________ 1978 Z28 T-Roof 1984 Berlinetta 2007 Solstice Supercharged 2014 C7 Z51 2020 RS Convertible 2023 2SS Convertible

06-09-2023, 10:54 PM	#5
MRBLIV Drives: 2023 Camaro 2LT Join Date: Jun 2023 Location: UT Posts: 1	This is the only thing I have found that is close to what I was experiencing. Right after start i hear a single clunk... Thing is brand new like I don't have my license plate new yet. Only happens on cold starts or right after a short drive. I have a video with a clear loud clunk. What was the fix or what was determined. Sorry just a bit paranoid haha. 2023 Camaro V6 A10 Last edited by MRBLIV; 06-09-2023 at 10:56 PM. Reason: Video did not upload

06-14-2020, 08:27 PM	#2
Yellow Beast TD Drives: 2017 2SS, 2014 Mercedes C300 Join Date: Feb 2020 Location: Connecticut Posts: 248	Take it in if you really think its an issue. Leave it until they hear it. The car is new! We'd be guessing unless you post a video.

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