03 4.6 Loud engine knock caused by roller rockers
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Northstar Engines and System Technical Discussion Discussion, 03 4.6 Loud engine knock caused by roller rockers in Cadillac Engine Technical Discussion; I started hearing a very loud knocking noise coming from the engine, especially when cold that sounded like a rod ...
  1. #1
    ltmax is offline Cadillac Owners Member
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    03 4.6 Loud engine knock caused by roller rockers

    I started hearing a very loud knocking noise coming from the engine, especially when cold that sounded like a rod bearing or carbon, and the car started missing and was way down on power.

    Tried all the usual recommendations for removing carbon etc but nothing worked. When I finally gave in and started tearing the engine down, I discovered three of the four roller rockers were not in place under two cylinders on the exhaust valves on rear bank of the motor.

    The rockers weren't damaged and nothing was loose or worn, and as soon as I loosened up the exhaust cam and placed the rockers back in position and put it all back together, the noise was gone and it runs great again.

    Has anyone else experienced this problem? I don't understand how these roller rockers could come loose and get spit out from under the camshaft.

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    eldorado1 is offline Cadillac Owners Connoisseur
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    That would point to a problem with the lash adjusters. Could be a blockage in the oil feed line, preventing them from getting oil pressure. Or even something as simple as bad oil... Don't be surprised if it comes back.

  4. #3
    AJxtcman's Avatar
    AJxtcman is offline Cadillac Owners Connoisseur
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    It will be back.
    was it #5 or #7?

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    ltmax is offline Cadillac Owners Member
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    I'm not sure how the northstar cylinders are laid out numerically, but it was both roller rockers on the exhaust valve for the third cylinder in counting over from the passenger side, and one roller rocker from the second exhaust valve over.

    What do I need to do to make sure this doesn't happen again?

    The motor only has 75k on it and no signs of wear on anything and it runs great.

  6. #5
    Highline Cady's Avatar
    Highline Cady is offline Cadillac Owners Fanatic
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    You can fix it by putting in new pistons. That's the GM fix for that. Then it'll knock all the time though.

  7. #6
    ltmax is offline Cadillac Owners Member
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    Maybe I'm misunderstanding something, I don't understand how roller rockers coming off inside the cylinder heads equates to needing replacement pistons, do you mean the lash adjusters under the overhead cams or do you thing that the pistons are hitting the exhaust valve and causing this?

  8. #7
    AJxtcman's Avatar
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    rear head?

  9. #8
    ltmax is offline Cadillac Owners Member
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    yes, rear head middle two exhaust valves, both rockers on one and one on the other

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    ltmax is offline Cadillac Owners Member
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    yes, rear head middle two cylinder exhaust valves, both rockers on one cylinder and one of two on the other

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    Re: 03 4.6 Loud engine knock caused by roller rockers

    We have had just a few with a strange rattle at times. Comes and goes. The last one I had I did a carbon treatment and the engine blew up right after. I had troubles turning the engine over by hand with the plug out before I started it after the carbon treatment. We have a sucker machine and I kept sucking crap out of #7 until it would turn over by hand. Then it poked a hole in (I think) the head. So that got an engine. I think that was #3 for this strange noise.
    This brings me up to last Thursday. I have an engine apart currently. I found a similar noise as before. I have no misfires. I think the Exhaust valves on #5 cylinder are hanging form time to time, but I have NO misfires. That would be very odd. If the Exhaust valves hang the followers would fall out. I will keep you posted on my findings.

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    Highline Cady's Avatar
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    Honestly I scaned this thread, I also have an 03 that knocks, and was told by the dealer the fix would be new pistons, maybe my knock is different than your knock, but that then it would knock all the time. That's all. Just relaying what I was told, like I said my knock might be diferent than your knock. Good luck either way.

  13. #12
    AJxtcman's Avatar
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    Quote Originally Posted by Highline Cady View Post
    Honestly I scaned this thread, I also have an 03 that knocks, and was told by the dealer the fix would be new pistons, maybe my knock is different than your knock, but that then it would knock all the time. That's all. Just relaying what I was told, like I said my knock might be diferent than your knock. Good luck either way.
    This is like that noise from the SLS that I was working on that blew up the day you were over. It was a few months ago. The motor expired in the shop. It had something floating around in it.

  14. #13
    ltmax is offline Cadillac Owners Member
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    I'm glad I caught mine when I did, there was absolutely zero damage to the top end, I just hope that we can figure out how to prevent this from happening again.

  15. #14
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    Someone should at least, for education purposes, tell the guy that there are not rocker arms in a 2000+ N*

    They're described as cam followers. It's not the same. No pushrods, no lifters.
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    ltmax is offline Cadillac Owners Member
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    Re: 03 4.6 Loud engine knock caused by roller rockers

    Oops, guess I'm showing my age, not quite up to speed on the OHC terminology. Thanks for the info, I added cam followers to the search thread and I'll try to edit the description thread if I can.

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