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Engine Knock Noise (need halp!)

This is a discussion on Engine Knock Noise (need halp!) within the General Help forums, part of the LSx Technical Help Section category; Honestly there are so many different noises in a LS1 its very hard to say what noise is which BUT ...

  1. #21
    Honestly there are so many different noises in a LS1 its very hard to say what noise is which BUT i can tell you most i've heard ALL have piston noise at start up. That sounds like a light diesel engine sound. Its barely noticable and usually is cased by carbon on the pistons. PISTON SLAP on the other hand is a LOUD HOLLOW knock that starts about 30 seconds after the engine starts, it usually lasts about 5 mins then its gone till the next cold start.

    Rod or wrist pin noise is not very noticeable cold but gets MUCH worse hot as the oil thins out. Of course rod bearing noise will cause the oil to turn silvery looking from the bearing material shedding into the oil.

    LIFTER NOISE<this is the LS1's bane of noises. Its the most common and i can tell you EVERY LS1 that gets run hard will have it. Its that ticking clatter chatter knocking slapping nasty azz noise you hear all the time.

    NOW the dealers will almosr ALWAYS say the lifter noise is piston slap, this lets them off the hook to fix your noise.......DEALER SUCK and will eat your wallet and are bottom feeding pricks!

    I'll bet you there are only a hand full of REAL piston slap engines out there. When you hear it you will know it from what described above.

    A normal ls1 will sound a little tappy light knocking diesel noises that gets much quieter warmed up completely. ANYTHING ELSE means its got some issues.
    Last edited by 99RTA; 07-09-2009 at 07:45 PM.

  2. #22
    Quote Originally Posted by chris777 View Post
    Please read, let me tell you a short story.
    Bought a gorgeous white WS6. Exterior and Interior are flawless. 48k miles. 2owners. Bought it for 14.5$.

    Problem is the previous owner got it when he was 17. Had it for 4-5years. 1day later I took it in to get oil changed because i had a LOW OIL light come on.(wasn't and isn't low on oil). They said they heard a ROD KNOCK. He said it was soft and inconsistant, if i just used synthetic oil, i shouldn't need to rebuild it or get a new engine or anything. After learning about piston slap and different LS1 engine noises, i felt a little better. A week ago my check engine light came on. Took it back, hooked up computer, it was a "knock sensor". So I talked to a different mechanic who referred me to another guy who works on drag cars, and corvettes and things. He just looked at it and called me today saying there is definitely engine noise. He thinks it's a piston not a rod, but that doesn't matter, it's still very bad, and needs fixed. Rebuilt or a new/used engine dropped in there. He said just using synthetic oil might make it last a little longer, but not much. and FYI..my oil pressure is always good, and I'm not 100% that any mechanic has listened to it after it's been running for awhile. They all heard it cold...but still...they should know the difference right? He also mentioned something was "worn smooth", which basically proved that the person before me RAN IT HARD.
    So my problem is
    1) If it's a piston and not a rod...is it really that bad?
    2) If i don't replace or rebuild, how much life do i have left?
    3) If i do replace or rebuild, which should i do, and how much $ am i looking at?
    4) Should i go kick this guys ass...and seriously...can i SUE him..this is BS!
    I'll give you some fee advice.....just drive it and forget about the noises unless you like throwing money away. LS1 engines are noisy so get used to it and relax. When you have a real problem noise you will know trust me.

  3. #23
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    2000 Corvette Convertable

    Mine Knocks Also

    I have the same problem with my 2000 Corvette LS1. It knocks a lot when cold then seems to quit down but not completely go away when warm. I read on another website that the rear knock sensor may be the problem. That could be true but I also thought that going to one range colder on the spark plugs may help. It would seem logical that compression is higher when the engine is cold which could lead to pre-detonation. Any input here could be useful. Thanks.

  4. #24
    Moderator Cutlass's Avatar
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    Quote Originally Posted by 2000 Red Vet Convert View Post
    I have the same problem with my 2000 Corvette LS1. It knocks a lot when cold then seems to quit down but not completely go away when warm. I read on another website that the rear knock sensor may be the problem. That could be true but I also thought that going to one range colder on the spark plugs may help. It would seem logical that compression is higher when the engine is cold which could lead to pre-detonation. Any input here could be useful. Thanks.
    Well unfortunately, none of that really makes sense for fixing your knock problem. Well maybe it does if your engine is pinging/detonating under load. But if its just knocking all the time, then its not related to the knock sensors, spark plug heat range, or compression.

  5. #25
    Retired NOT tired SteveC's Avatar
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    2001 Z28 (Sara)

    The piston slap is caused by the steel sleeving around the piston bore, when cold the disimilar metals expand at different rates. I have the piston slap when cold, and a light uneven ticking when warm, my mechanic (a hot rodder) attributes the latter to the roller bearings on the lifters.

    I have 28K on my engine (original miles), and the vehicle performs wonderfully.

    I have heard rod knocks before, and believe me you would know it, it would be a constant LOUD banging that gets faster with RPM's.

    If you have a faint uneven ticking when warm, I would not worry about it, if it is something bad, the noise will get worse, my faint uneven ticking has been going on for 15K, and has never gotten louder or constant.

    SteveC

  6. #26
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    2000 Corvette Convertable

    Thanks Steve, the detectable knock when cold and inconsistant light knock periodically when warm is what I am hearing - mostly under light throttle. I'll let it go and not run it hard when cold.

  7. #27
    Senior Member JayTA98's Avatar
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    could it be possible for someone to post a video of piston slap noise? I would but I dont have piston slap yet. I think it will be great for a lot of people to be able to hear it.

    I have the ticking noise when the car is under load. I have been driving my car for like 2 yrs now. I was like you the at the beginning when I got it but as I learned more about these cars I don't worry that much.

  8. #28
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    I don't have a video but mine sounds like a diesel engine when cold and then it goes away. Other posts indicate that this is piston slap.

  9. #29
    Member DaddySS's Avatar
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    If you have good oil pressure, the engine runs fine, etc. the chances are that it is just normal noise from an aluminum block engine. Keep the oil changed and checked with good oil, don't use FRAM filters, replace the knock sensors, drive it and enjoy it.

  10. #30
    Junior Member black2kSS's Avatar
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    yup on the first start up i get a nice slap out of it, even at 25k. sucks but hey the sound of the tires screaming after she warms up NEVER bothers me a bit

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