Page 2 of 3 FirstFirst 123 LastLast
Results 21 to 40 of 46

Loud Engine Knock at Cold

This is a discussion on Loud Engine Knock at Cold within the General Help forums, part of the LSx Technical Help Section category; Originally Posted by tatertot91 still sounds like a spun rod bearing, very common to hear the noise you're hearing and ...

  1. #21
    Member importhater81's Avatar
    Join Date
    Oct 2009
    Location
    chicagoland,Il
    Age
    36
    Posts
    333

    black
    02 ss camaro

    Quote Originally Posted by tatertot91 View Post
    still sounds like a spun rod bearing, very common to hear the noise you're hearing and then it going away after it heats up. I would open the motor up if your neighbors have commented on it. Sounds too loud for piston slap.
    A spun rod bearing wouldn't quiet down after it is warmed up,neither would a cracked flywheel.

    Most likely a lifter that bleeds down and takes a while to prime up,or piston slap.

  2. #22
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,998

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    ^^^^ Yep 100% agree. I wonder if it could also be excessive carbon buildup? Some of the Cadillac Northstars have a cold start knock because of excessive carbon build-up. You could try to run a top engine cleaner through the engine.

  3. #23
    Member DaddySS's Avatar
    Join Date
    Oct 2005
    Location
    Bergen Co. NJ
    Posts
    590

    Black
    2000 Camaro SS Conv.

    Both good thoughts.

    The fact that it changed volume when the rocker was loosened is interesting - could support the lifter thoery.

  4. #24
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    Alright, I started posting in another thread about this, but I will summarize here.

    I now have 185000 on the car and the knock is still there. I am looking for any other ideas of what it might be.

    I have done the following:
    1. Replace the lifters with LS7 lifters and LS2 carriers. Also replace head gaskets, exhaust gaskets, knock sensors, oil sensor, intake gaskets, valve cover gaskets, oil, belts, antifreeze. Also removed all carbon buildup from pistons.

    Still had the noise plus rocker chatter.

    2. Replace stock push rods (7.4") with Comp Cams push rods (7.35") after measuring and adding 0.075" for preload.

    No more rocker chatter, but still have the noise. Here is a video:



    Here are some images from the lifter change:

    523100_10151071035881939_845039931_n.jpg
    598753_10151072052316939_777831947_n.jpg
    598853_10151072051316939_1596798306_n.jpg
    310574_10151072052626939_1460072720_n.jpg
    Last edited by Loser; 01-30-2013 at 09:47 PM.

  5. #25
    Senior Member redbird555's Avatar
    Join Date
    Mar 2009
    Location
    pompano beach florida
    Age
    27
    Posts
    1,008
    2002 Camaro Z/28 Pewter

    Quote Originally Posted by Loser View Post
    Alright, I started posting in another thread about this, but I will summarize here.

    I now have 185000 on the car and the knock is still there. I am looking for any other ideas of what it might be.

    I have done the following:
    1. Replace the lifters with LS7 lifters and LS2 carriers. Also replace head gaskets, exhaust gaskets, knock sensors, oil sensor, intake gaskets, valve cover gaskets, oil, belts, antifreeze. Also removed all carbon buildup from pistons.

    Still had the noise plus rocker chatter.

    2. Replace stock push rods (7.4") with Comp Cams push rods (7.35") after measuring and adding 0.075" for preload.

    No more rocker chatter, but still have the noise. Here is a video:



    Here are some images from the lifter change:

    523100_10151071035881939_845039931_n.jpg
    598753_10151072052316939_777831947_n.jpg
    598853_10151072051316939_1596798306_n.jpg
    310574_10151072052626939_1460072720_n.jpg
    that sounds like piston slap, and if it were anything serious the motor sure would have let go a long time ago since you've put 30000 more miles on it. there is no way to get rid of the slap but it will not hurt the motor, unless you completely tore it down bored it out and put new pistons in it will always be there. and even if you do new pistons the noise may still be heard as the short ls piston skirt design rocks in the bore causing slap just by nature of the design.

  6. #26
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    10,511

    Navy Blue Metallic
    98 T/A w/a little mods...

    Quote Originally Posted by Loser View Post
    Alright, I started posting in another thread about this, but I will summarize here.

    I now have 185000 on the car and the knock is still there. I am looking for any other ideas of what it might be.

    I have done the following:
    1. Replace the lifters with LS7 lifters and LS2 carriers. Also replace head gaskets, exhaust gaskets, knock sensors, oil sensor, intake gaskets, valve cover gaskets, oil, belts, antifreeze. Also removed all carbon buildup from pistons.

    Still had the noise plus rocker chatter.

    2. Replace stock push rods (7.4") with Comp Cams push rods (7.35") after measuring and adding 0.075" for preload.



    What did you measure the push rod length with? The Comp Cams checker? Important to know because of the checker's length.

    How many turns did you get?

    I need to know so I can tell if your math is correct. No offense just some get the procedures wrong.





    I responded to your other thread, its best to keep it all in one thread, having multiple threads gets you more exposure but also can leave important details out of them too.

  7. #27
    Moderator 35th-ANV-SS's Avatar
    Join Date
    Oct 2008
    Location
    Wherever life takes me
    Posts
    12,465

    Red
    02 35th LE Camaro SS

    Never heard piston slap that loud before. Glad my LS motor is quiet. That push rod length is odd.
    It's on jackstands.

  8. #28
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    Quote Originally Posted by SMWS6TA View Post
    What did you measure the push rod length with? The Comp Cams checker? Important to know because of the checker's length.

    How many turns did you get?

    I need to know so I can tell if your math is correct. No offense just some get the procedures wrong.





    I responded to your other thread, its best to keep it all in one thread, having multiple threads gets you more exposure but also can leave important details out of them too.
    Yes. 6.8 + 9.5 turns * 0.05" = 7.275" + 0.5"(preload) = 7.325" (but I used 0.075" preload with 7.35" push rods since that is what I have seen other people using when I searched around the Web)

    I have two threads because in the other thread I was just trying to understand the method of adjusting the rocker arms, then it evolved back into the engine knock issue which is the subject of this thread. So I will work with this thread moving forward unless a Moderator would rather merge the threads (up to them).

    Anyway, since I removed the heads and replaced the lifters, push rods, gaskets etc. and, when I adjust the rockers i can make the rocker chatter change but not impact the knock sound at all, I think the knock is not related to the lifters, push rods, rockers, or valves. Note that when I removed the heads, there didn't appear to be any valve damage. It seems that this knock is something deeper in the motor.
    Last edited by Loser; 01-31-2013 at 11:15 AM.

  9. #29
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    Quote Originally Posted by SMWS6TA View Post
    way to loose



    I have a few questions:

    The videos are done at idle, have you rev the rpms up to 2-2.5k ? If so does it increase the frequency of the noise (not the loudness)?


    I see you stated you installed LS7 lifters so I'm trying to confirm that you did.

    If you pulled the heads off have you had them check the valves for vacuum leaks? I had mine check when I pulled mine off and the #4 cylinder intake valve need to get lapped because it failed on the pressure check.

    When they were off did you have the heads milled? If so how much?

    Gaskets - reused or replaced? Using the stock thickness?

    The last two really matter when it comes to PTV clearances.



    The 3rd video sounds very close to mine but so much clearer.... I order 7.325 push rods that should be coming in today. If they do I'll be working on it tonight. I hope it fixes it.
    This is a reply to your message in the other thread Trying to adjust rocker arms on 2001 Trans Am WS6

    Yes, as I rev the motor, it increases in frequency but not loudness.

    I did not have the valves checked or the heads milled, but I did use new gaskets. I'm not sure if they were stock thickness.

  10. #30
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    10,511

    Navy Blue Metallic
    98 T/A w/a little mods...

    Quote Originally Posted by Loser View Post
    Yes. 6.8 + 9.5 turns * 0.05" = 7.275" + 0.5"(preload) = 7.325" (but I used 0.075" preload with 7.35" push rods since that is what I have seen other people using when I searched around the Web)
    ok I hope this bold above was a type o...

    9.5 turns x 0.050" = 0.475" + 6.8" = 7.275" + 0.5" = 7.775" (I'm not trying to be a dick here, just showing you everything so you can see and others can follow)

    Your preload corrected to 0.050" not 0.5"

    7.275" + 0.050" = 7.325"

    LS7 Lifters preload (*see note below) is 0.075"

    7.275" + 0.075" = 7.350"


    If this helps I'm in the same boat as you, I bounced off the rev limiter around Thanksgiving during a burn out and mine has been making the same noise as yours. I chased it the same way as you too, thinking bent push rod or bad lifter. I did do a vacuum test on my heads since they were off and only cost me $20 including the lap job on on valve. I should have been charged more for him milling the heads a "little bit" (his words) but 1. he didn't ask me before he did them & 2. his desk jockey forgot to tell me when I picked them up. I found out after the heads were on and I still had noise. I went back to him to find out because I needed to make sure in case I needed to change my PR length. Turns out I did, I measured out at 7.325".

    A few thousands can make a major difference on how everything works. A few too long can bind the springs up, this causes them to compress without any spacing, over time at high rpms it will break them.



    * note: there has been lots of discussion on the LS7 lifters preload on the other site. TS&P, Thunder racinig and a few others have come out stating that the LS7 lifter while total outside legnth measures the same as a LS1, the cup position in the LS7 sits higher then the LS1. This difference is what is causing some to have issues with the LS7 lifters like broken springs, bent rods and even the lifters themselves going bad after a few thousand miles. The really scary part is it can also lobe a cam too.

    To be fair GM still states to use 7.4" rods with stock heads but alot of that depends on cylinder height (milled or not) aftermarket rollers, etc.


    Quote Originally Posted by Loser View Post
    I have two threads because in the other thread I was just trying to understand the method of adjusting the rocker arms, then it evolved back into the engine knock issue which is the subject of this thread. So I will work with this thread moving forward unless a Moderator would rather merge the threads (up to them).

    Anyway, since I removed the heads and replaced the lifters, push rods, gaskets etc. and, when I adjust the rockers i can make the rocker chatter change but not impact the knock sound at all, I think the knock is not related to the lifters, push rods, rockers, or valves. Note that when I removed the heads, there didn't appear to be any valve damage. It seems that this knock is something deeper in the motor.
    No problem just trying to help here.



    Like I said above I'm right there with you. Me ordering the new push rods is my last stop gap prior to pulling the motor. Cause if this doesn't fix it it means the following:

    Bearings (crank, cam, connecting rods) - one of them is going.
    piston pin - coming loose

    All of these require pulling the motor to get a look at.

  11. #31
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    Quote Originally Posted by SMWS6TA View Post
    ok I hope this bold above was a type o...

    9.5 turns x 0.050" = 0.475" + 6.8" = 7.275" + 0.5" = 7.775" (I'm not trying to be a dick here, just showing you everything so you can see and others can follow)

    Your preload corrected to 0.050" not 0.5"

    7.275" + 0.050" = 7.325"

    LS7 Lifters preload (*see note below) is 0.075"

    7.275" + 0.075" = 7.350"


    If this helps I'm in the same boat as you, I bounced off the rev limiter around Thanksgiving during a burn out and mine has been making the same noise as yours. I chased it the same way as you too, thinking bent push rod or bad lifter. I did do a vacuum test on my heads since they were off and only cost me $20 including the lap job on on valve. I should have been charged more for him milling the heads a "little bit" (his words) but 1. he didn't ask me before he did them & 2. his desk jockey forgot to tell me when I picked them up. I found out after the heads were on and I still had noise. I went back to him to find out because I needed to make sure in case I needed to change my PR length. Turns out I did, I measured out at 7.325".

    A few thousands can make a major difference on how everything works. A few too long can bind the springs up, this causes them to compress without any spacing, over time at high rpms it will break them.



    * note: there has been lots of discussion on the LS7 lifters preload on the other site. TS&P, Thunder racinig and a few others have come out stating that the LS7 lifter while total outside legnth measures the same as a LS1, the cup position in the LS7 sits higher then the LS1. This difference is what is causing some to have issues with the LS7 lifters like broken springs, bent rods and even the lifters themselves going bad after a few thousand miles. The really scary part is it can also lobe a cam too.

    To be fair GM still states to use 7.4" rods with stock heads but alot of that depends on cylinder height (milled or not) aftermarket rollers, etc.




    No problem just trying to help here.



    Like I said above I'm right there with you. Me ordering the new push rods is my last stop gap prior to pulling the motor. Cause if this doesn't fix it it means the following:

    Bearings (crank, cam, connecting rods) - one of them is going.
    piston pin - coming loose

    All of these require pulling the motor to get a look at.
    Yes, I meant 0.05". Oops.

    I've had the knocking noise now for about 40,000 miles total. If you do dig into the motor, let me knw what you find. I may end up doing the same thing.

  12. #32
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    I took the car for its first drive after changing the push rods. After about 15 miles of driving, it quieted down completely. Now at idle, when hot, my oil is at about 40PSI instead of 60PSI and I don't hear any knocking or clattering. I'm going to let it cool down and see if the knocking comes back when it is cold still.

  13. #33
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,998

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    Based on the speed of the knock and the fact that you replaced about everything valve train related, I'm thinking it *could* be a camshaft bearing knock. The knock seems to be half of crankshaft speed, which eliminates mains, rods, cracked flywheels, loose torque converter bolts, harmonic balancers, belt driven accessories, oil pump, etc as a source of the knock. But its so hard to tell from a youtube video.

    If you rev it up a little, does it double knock? rods and piston pins double knock with a light rev.
    -------------------------------------
    Kooks 1 7/8" race headers, Kooks ORY, Borla catback, Nitto 555R, LS6 intake manifold, Shaner S3 ported stock throttle body, SLP lid, smooth bellows, JAAM Ram Air kit, Elite Engineering catch can, LS6 valley cover, EGR and AIR deleted, Frost tune, and Simpson Racing child car seat in the back. 13.2 @ 108MPH

  14. #34
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    Quote Originally Posted by Cutlass View Post
    Based on the speed of the knock and the fact that you replaced about everything valve train related, I'm thinking it *could* be a camshaft bearing knock. The knock seems to be half of crankshaft speed, which eliminates mains, rods, cracked flywheels, loose torque converter bolts, harmonic balancers, belt driven accessories, oil pump, etc as a source of the knock. But its so hard to tell from a youtube video.

    If you rev it up a little, does it double knock? rods and piston pins double knock with a light rev.
    Here is a video where I am rev'ing up the motor:


  15. #35
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,998

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    it does kinda double knock, doesn't it? Hmmm, not good.

  16. #36
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    Quote Originally Posted by Cutlass View Post
    it does kinda double knock, doesn't it? Hmmm, not good.
    But it goes away completely after it warms up

  17. #37
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,998

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    yeah, there's no way that's a rod knock or piston pin knock. I listened to it on another computer and it almost sounds like 2 noises. When you rev it, it sounds like there is an exhaust leak-tick, but I do still hear a 1/2 crank speed valve train type noise.

  18. #38
    Moderator Cutlass's Avatar
    Join Date
    Apr 2008
    Location
    Madison, WI
    Posts
    6,998

    1999 Formula WS6 M6-sold
    2001 Silverado Z71

    Quote Originally Posted by Loser View Post
    But it goes away completely after it warms up
    how long of a warm up does it take? Noises that go away with warm up include: piston slap, exhaust leak, and sometimes lifters if they don't pump up fast.

  19. #39
    Spaz is My Mentor SMWS6TA's Avatar
    Join Date
    Feb 2009
    Location
    Ugy Lower Corner of AL
    Posts
    10,511

    Navy Blue Metallic
    98 T/A w/a little mods...

    Quote Originally Posted by JRENIGAR View Post
    My car had this problem, turned out to be a cracked flywheel!!!! I mean it sounded just like a knocking engine. Hope this is your problem, and not the rods or bearings...
    Can you expand on this, by that I mean did you feel anything with the clutch (if you are a M6)

  20. #40
    Junior Member
    Join Date
    Apr 2010
    Location
    Gilroy, CA
    Posts
    59

    Black
    2001 Trans AM WS6

    Hi, sorry for the delay in responding. Work got really busy. Anyway, I have a couple thousand more miles on the car now. The noise is still there and no longer goes completely away when it warms up. The volume goes down to about 20% of what it was at cold, but I can still hear it at warm. I'm going to pull the valve covers today and make sure everything still looks fine there.

    As per feeling anything in the clutch, this car is an automatic. I do feel a thumping in the gas pedal as the car warms up now. This is a new symptom over the last month or so. It is at the same frequency as the banging noise in the motor.

Page 2 of 3 FirstFirst 123 LastLast

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Help: loud valvetrain squeak at cold start
    By dethinboots in forum GTO
    Replies: 13
    Last Post: 01-16-2016, 08:55 AM
  2. knock knock...who's there? wait...engine knock...
    By jiveass in forum Internal Engine
    Replies: 60
    Last Post: 04-26-2011, 08:04 AM
  3. Help: LOUD engine knock
    By Rhinohuey in forum Firebird / WS6
    Replies: 6
    Last Post: 01-31-2009, 08:11 PM
  4. Engine has knock when cold
    By rel3rd in forum Internal Engine
    Replies: 12
    Last Post: 07-09-2007, 09:23 PM
  5. cold start up knock?
    By eric69cam in forum GM Trucks
    Replies: 5
    Last Post: 11-13-2006, 06:51 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •