Brief Cold Start Knocking/Tapping? *Video*
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Instructor
Joined: Mar 2023
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2023 C6 of the Year Finalist - Unmodified
Brief Cold Start Knocking/Tapping? *Video*
Just trying to see if anyone has heard this exact noise before. Only last 1-2 seconds, it’s inconsistent. Some cold starts it doesn’t make this noise, sometimes is only knocks once or twice, sometimes multiple times.
Is this just a lazy lifter bleeding down? Piston slap? Oil psi is great. Just changed my oil and the noise keeps getting quieter and more brief like it’s going away. These clips are from before the change. Thanks!
Is this just a lazy lifter bleeding down? Piston slap? Oil psi is great. Just changed my oil and the noise keeps getting quieter and more brief like it’s going away. These clips are from before the change. Thanks!
Melting Slicks
Joined: Apr 2019
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From: Northern Wisconsin
Maybe timing chain slap? You don't say which engine you have. LS7's don't generally have timing chain slap due to the design of their chain guide, but the chain guides on some of the other engines can fail and cause slap.
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Instructor
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2023 C6 of the Year Finalist - Unmodified
My bad! It’s an LS3. I have a 2008 Base with 135,000 miles.
Burning Brakes
Joined: Jun 2020
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From: San Jose, CA
2023 C6 of the Year Finalist - Unmodified
2022 C6 of the Year Finalist - Unmodified
I don’t think that’s piston slap. It doesn’t typically go away that quickly. Piston slap usually is because the engine is cold. This noise goes away after a couple of seconds. It implies that it is oil pressure related. Probably lifters that are bleeding down.
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Le Mans Master
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While my 2008 does not make that noise (27,000 miles), I can say that I had a Crown Vic (my business car) that made that exact temporary noise on start up after an oil change when the shop put on one of their generic oil filters that didn't have the adequate bypass valve system to allow oil to flow quickly on a cold start. Went to a different filter/shop and the noise went away. Just a thought.
Racer
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From: San Antonio, Texas
Burning Brakes
Joined: Jun 2020
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From: San Jose, CA
2023 C6 of the Year Finalist - Unmodified
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Racer
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From: NV
I had a '99 Camaro SS Z28 with the LS1 and T-56 in it with piston slap. Beat the living **** out of that car at the drag strip, road coarse, street and tried to kill it under warranty and it never happened. The slap did not sound like that at all. Your metallic sounds more like rod knock than piston slap.
It could also be valve train but pretty deep and thick noise for that. It could be starving for oil on startup, but if you turn it off after its good and oiled with correct pressure and right back on again it should be oiled and if it doesn't make the noise then it could be lack of oil.
It could also be valve train but pretty deep and thick noise for that. It could be starving for oil on startup, but if you turn it off after its good and oiled with correct pressure and right back on again it should be oiled and if it doesn't make the noise then it could be lack of oil.