The engine has developed a knock
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2004-2007 Cadillac CTS-V General Discussion Discussion, The engine has developed a knock in Cadillac CTS-V Series Forum - 2004 - 2007; A little back story, because I like to tell a story. Bought a season pass to the drag strip, opening ...
  1. #1
    carsaremytoys is offline Cadillac Owners Member
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    The engine has developed a knock

    A little back story, because I like to tell a story. Bought a season pass to the drag strip, opening day is today. Fire the beast up this afternoon and I hear a slight knock, most people wouldn't hear it. I blow it off. Get to the track and take a breather and gather my bearings because I'm still getting used to 600+hp, hopping on the freeway I gave it in 3rd gear and I got the "traction engaged" message! Not bragging, but more adrenaline rushes when I drive this car than the 150hp (02 suzuki gsxr 750) sport bike I used to know as the only thing to get my adrenaline going. Ten minutes pass and I get in line, I'm two cars to the tree sitting next to a building with my window down, I hear the knock echoing off said building. I ask the traffic director "Is that me" he replies, "yes". I ask how to leave and he tells me to pull out through an opening, and states "don't blow it up"

    We first thought rocker, but it may also be a bearing in the charger. It's not a bad knock, but it got worse from the drive there (20 miles) so I know it is something.
    I have yet to tear into an engine, so I don't know much about them. I still have 30+ lbs of oil pressure at idle, I don't think it's that big of a deal, but, like I said, I haven't torn into an engine and have no idea what I'm getting into.

    I know my description isn't much to go by, here is a video I took earlier today (before I left for the track). You probably won't hear the knock (drivers side is where it sounds like it's coming from) but I'm trying to give as much info as I can.

    http://www.youtube.com/watch?v=7k-eyBRWH2c

    I plan to get another video when I take the stethoscope to it to hopefully find out where it's coming from. I don't want to fire it up if I don't have too.

    What I know about the heads is:
    Ported and polished by BES engines
    Patriot Gold Dual springs and Ti retainers
    Comp cams 7.450 pushrods with Yella Terra rockers

    I will ask the previous owner if he can find out more about who did the work (the guy he bought it from had the work done).

    For those who want to help me figure this out, but don't know the car:

    http://www.cadillacforums.com/forums...ought-one.html

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    izcain's Avatar
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    Re: The engine has developed a knock

    Pull the covers and take a look at it.

    When you bought the car I assumed you pulled the tune and made sure it was safe before boosting on it right?

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    robojesus is offline Banned
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    Re: The engine has developed a knock

    what's the worst that would happen if you took your belts off that supercharger for a minute? that doesn't exactly sound like rod knock, but that could be your phone. maybe a collapsed lifter? any misfiring?
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    carsaremytoys is offline Cadillac Owners Member
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    Re: The engine has developed a knock

    I didn't pull the tune, I was assured numerous times by the seller that it is tuned for safety. I'm set up to have it towed to a speed shop tomorrow. I will most likely have them dyno tune it (after they fix it). I just had my neighbor have a listen and made a small video. The beginning of the video is of the drivers side of the engine and then moves to the passenger side. The noise sounds like it's coming from the drivers side.

    http://www.youtube.com/watch?v=***0IYKQGMQ

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    Re: The engine has developed a knock

    link no worky

  7. #6
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    Re: The engine has developed a knock

    the frequency of it should tell you something--crank- vs cam-centric (not official terms; made up by me just now)

    ...or ignition-centric.

    ...the crank turns twice for every revolution of the cam. the pistons and rods are tied to the revolutions of the crank, and everything in the upper half (heads/valves) are tied to the revolutions of the cam.

    and if it only happens during a spark/cylinder ignition, that's significant as well. you can isolate that by disconnecting plugs one at a time.

    you can also get yourself a cheap listening tool, basically an aluminum rod that will allow you to localize the sound by touching it to different parts of the engine

    to get the most accurate indicator of the revolutions of the crank, use a timing tool that flashes a light at every ignition of one of the cylinders. a flashing light is easier to interpret than trying to keep track of the markings on the harmonic balancer with the un-aided eye.

    it's pretty easy to tell whether a sound is at the same frequency as the timing light, or twice as frequent (or another rate altogether/irregular)

    also check for a smell in the exhaust. oil smells like burned oil, coolant smells like... burned cat urine-ish.

    //I just had a listen, that's more of a rattle, sounds rather irregular. how does it change with increased RPMs? (sort of a two-person job, one person to man the camera/mic).

    Quote Originally Posted by izcain View Post
    Pull the covers and take a look at it.

    When you bought the car I assumed you pulled the tune and made sure it was safe before boosting on it right?
    who pulls a tune? the man admitted he's never torn an engine apart. he's here for help. what would you do with a tune, izcain? do you know how to read one? do you know someone who does?

    like you wouldn't jump on a V with that motor in it, as long as it sounded fine. I would, no doubt in my mind.

    //...wait. is it for sale? (discount for the noise?) :-D I'm such a dick. I'm just teasing, I think it's gonna be OK--I was expecting worse--like, an obvious knock due to blow-by (gouges in the cylinder walls).

    truth be told, I don't have any personal experience with valvetrain failures nor have I heard them first-hand, so I am not qualified to say it isn't a pushrod or broken spring, or anything else loose under the valve covers (especially not from here). I've had everything else go wrong with engines of mine, though.

    I was at one time long ago, an ASE cert-holding Air Force mechanic.

    //izcain is just mad that you have a super ****in' awesome car. I think he's one of those guys who can't just be -happy- for people who have nice things

    //so far it's been robojesus and izcain to the rescue. God help you

    where are you? Los Angeles area, by any chance? I have... nothing going on Fri-Sun (full-time student now. your mom goes to college!).

    oh nevermind. you're way up there. damn... that's you? shit, man, um...

    ok, to share exactly what I'm thinking, I am curious exactly how much driving you did on the motor before the sound started. I wonder this because there are things like Lucas oil products that will thicken the oil and hide sounds and symptoms temporarily, say, long enough to sell a car.

    I hope that's not the case... that the sale was driven by an imminent problem.

    maybe there's just a switch you missed in the cockpit, or you gotta jiggle the handle or something. (just don't jump through the phone at 'im! [especially not on account of what I just said about the Lucas oil])

    //I like stories, and humor. I was also a medic, and know that telling and relating to stories is an indicator of a favorable prognosis. having a name like robojesus is not.

    //k i'm done. I'm not always like this. it's only when I'm awake. sorry

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    Re: The engine has developed a knock

    I haven't revved it since the noise started, but it's consistent with idle. I drove it 600 plus miles home, the noise came only 50 or so miles after that. I don't believe the seller tried to screw me, he has numerous thousands into it to make it good in the few months he owned it. The oil was changed hundred or so miles before I Bought it with Mobil one. I was told to change the oil before taking it to a shop, I think I will do this. Any filters and weight recommendations? I'm not even sure how much or if The pan is still a stock ls 6 I'll get under it as soon as I have the chance.

  9. #8
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    Re: The engine has developed a knock

    man, I forgot about how loud the exhaust is.

    assuming:
    -your oil pressure is 30 idle/40ish above-idle,
    -you have fluid in the cooling system, and the temps are fine...
    -and you don't smell oil or coolant from the exhaust...

    try to:
    1: isolate the sound with the stethoscope,
    2: do this rev test (and get a recording of it):

    4k (midrange) and hold,
    then 5.5k (high-ish range) and hold.

    sounds are more telling as you raise the RPM. as the engine speeds up, the duration of all the actions in the motor are shortened... this causes some things to float, others to bang harder... the timing advances, and oil pressure rises... the balance of rotating parts can improve or worsen (temporarily, through the different RPMs).

    depending on the issue, the sound could simply speed up with the motor(in "lockstep"--you'll be able to tell, and it would indicate something linked directly to the crank or cam, and 2:1 crank to cam rotational ratio is key in determining that), but it could also get louder, get softer, or go away (indicating something secondary to the crank or cam, such as lifters, pushrods, rocker arms, springs, valves)

    so. a useful sound bite would be bumping the rpm a few times ("stoplight revs"), and holding it at 4k and then 5.5k-ish.

    doing it while rolling and accelerating under load might produce different results, as well.

    and then there's figuring out where it's coming from--high/low? front/back? left/right... also try unplugging the power to the coils one by one (isolate cylinder spark/ignition)

    also try disconnecting and reconnecting the battery to see if doing a "soft" reset of the computer makes the sound go away. (for the MAF and the speed density tune you have, which I'm not familiar with, but it's worth a try to "turn back" an error counter that the computer might have decided it had enough of--though 600 miles is a little long, and if what you say is accurate, the sound has grown louder...)

    If you could reduce the sound coming from the exhaust, -somehow- that would help with this endeavor. maybe extension pipes trailing out the back end of the car, and under the garage door... I don't have ideas for that one, other than something like an exhaust extractor (like they use in shops).

    It could also be something -really- simple, like loose exhaust flange bolts, or the headers coming loose from the block. aftermarket headers tend to come loose, constantly. exhaust leaks can sound like knocks but they'll also have a "putt putt putt" quality to it. see real quick if the sound is more noticeable under the car, nearer the transmission.

    I should invest in a code reader; I would like to hook one up for this. they're inexpensive and they make bluetooth enabled ones that remain plugged into your computer and will send real-time readouts to your smartphone.. sub-$100 range, if I recall correctly. Ebay, and I've seen auto parts stores carry them)

    lastly: do you still have full power out of the motor (has there been a noticeable drop in power)

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    Re: The engine has developed a knock

    I've never felt full power, I was nice on the drive home because I wanted to make it home, and I haven't turned off the traction control yet. I've been near full throttle, but for a very short time
    D3l7a3ch0 and D3l7a3ch0 like this.

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    Re: The engine has developed a knock

    D3,
    I applaud your efforts to help Matt. I can also understand why you would suggest Lucas oil being used to hide noise. I want to ensure you and Matt that this was not done. Actually, you can tell if Lucas was used by looking at the dipstick and even more so when changing the oil. I would not of spent over 5 grand on the car before selling it if I was trying to hide anything.
    To me, it sounds like lifter tic. There are common reasons for this. Deposits in the oil, bad lifter, low oil, or bent push rod. Although the oil had about 1k miles on it when he took it, I suggested he change it out and maybe put a slightly heavier weight in it just to ensure any deposits were not the issue. From there, taking off the valve covers to see where it is coming from is next.

    ----------

    I just read your comment about a loose header. That is a possibility also that I did not take into account. A long time ago, I drove one of my dad's hot rod's. I down shifted at a high RPM so they exhaust would pop. One too many times and it back-fired pretty loud. A similar noise, as a lifter would make, came afterwards. It ended up being a blown header gasket.
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  12. #11
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    Re: The engine has developed a knock

    D3, you crack me up.

    Actually, I had a header leak that may have sounded like this, but mine was more subtle, and my hearing wouldn't allow me to hear it though EVERYBODY else said they could. Had new gaskets put on, buttoned up really nice, and now it's quiet. The sound in your video does sound like that kind of leak, only more pronounced than mine. Sure wouldn't want you to undertake that kind of effort (and expense) unless you were pretty certain that's it, though.

    Question becomes how best to determine if it is a header leak. D3's "stethoscope" recommendation is probably the way to go. Even a portion of a doggone garden hose with one end at your ear and the other end moved around and positioned down near the exhaust ports might work. You just need to focus such a listening device at the location of the noise and get it to your ear to determine exactly where it's loudest then better problem identification can occur.

    My $0.02.
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    I know the stethoscope method is widely recommended but on a recent issue w an ls1 this proved to be ineffective for me. You could hear the tick everywhere. It turned out there was a bent pushrod, bad lifter, and damaged cam lobe. There really is no replacement for opening the engine and investigating.

    The garden hose should help to find exhaust leaks but if you have an aluminum block the stethoscope may not help localize the issue. Pulling the valve covers and checking for a bent pushrod and loose or failing rocker is pretty easy. Going further will likely require pulling the heads.
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    Re: The engine has developed a knock

    :-D

    I did not mean to offend! the thought crossed my mind "what if" the previous owner is on the forums, but I did not consider it would be an apache pilot (gimme a break! lol are you WO or O-type?)

    umm funny story about Rucker... anyway.

    I feel like I should have asked:
    -does it have solid lifters, or rollers, or hydraulic rollers...?
    -did you gain altitude between the sale location and your home, by any chance. I have never messed with timing on OBDII engines, but... what's that about advance--maybe you need more octane...... (what does the +1 advance mean/how was that accomplished, I wonder)

    what octane does it use? was there an explanation for the 8:1 compression and low boost? just curious

    there is a huge chance I am wrong about everything I say, but if I'm wrong, might as well be wrong strong

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    Re: The engine has developed a knock

    Quote Originally Posted by D3l7a3ch0 View Post
    the frequency of it should tell you something--crank- vs cam-centric (not official terms; made up by me just now)

    ...or ignition-centric.

    ...the crank turns twice for every revolution of the cam. the pistons and rods are tied to the revolutions of the crank, and everything in the upper half (heads/valves) are tied to the revolutions of the cam.

    and if it only happens during a spark/cylinder ignition, that's significant as well. you can isolate that by disconnecting plugs one at a time.

    you can also get yourself a cheap listening tool, basically an aluminum rod that will allow you to localize the sound by touching it to different parts of the engine

    to get the most accurate indicator of the revolutions of the crank, use a timing tool that flashes a light at every ignition of one of the cylinders. a flashing light is easier to interpret than trying to keep track of the markings on the harmonic balancer with the un-aided eye.

    it's pretty easy to tell whether a sound is at the same frequency as the timing light, or twice as frequent (or another rate altogether/irregular)

    also check for a smell in the exhaust. oil smells like burned oil, coolant smells like... burned cat urine-ish.

    //I just had a listen, that's more of a rattle, sounds rather irregular. how does it change with increased RPMs? (sort of a two-person job, one person to man the camera/mic).



    who pulls a tune? the man admitted he's never torn an engine apart. he's here for help. what would you do with a tune, izcain? do you know how to read one? do you know someone who does?

    like you wouldn't jump on a V with that motor in it, as long as it sounded fine. I would, no doubt in my mind.

    //...wait. is it for sale? (discount for the noise?) :-D I'm such a dick. I'm just teasing, I think it's gonna be OK--I was expecting worse--like, an obvious knock due to blow-by (gouges in the cylinder walls).

    truth be told, I don't have any personal experience with valvetrain failures nor have I heard them first-hand, so I am not qualified to say it isn't a pushrod or broken spring, or anything else loose under the valve covers (especially not from here). I've had everything else go wrong with engines of mine, though.

    I was at one time long ago, an ASE cert-holding Air Force mechanic.

    //izcain is just mad that you have a super ****in' awesome car. I think he's one of those guys who can't just be -happy- for people who have nice things

    //so far it's been robojesus and izcain to the rescue. God help you

    where are you? Los Angeles area, by any chance? I have... nothing going on Fri-Sun (full-time student now. your mom goes to college!).

    oh nevermind. you're way up there. damn... that's you? shit, man, um...

    ok, to share exactly what I'm thinking, I am curious exactly how much driving you did on the motor before the sound started. I wonder this because there are things like Lucas oil products that will thicken the oil and hide sounds and symptoms temporarily, say, long enough to sell a car.

    I hope that's not the case... that the sale was driven by an imminent problem.

    maybe there's just a switch you missed in the cockpit, or you gotta jiggle the handle or something. (just don't jump through the phone at 'im! [especially not on account of what I just said about the Lucas oil])

    //I like stories, and humor. I was also a medic, and know that telling and relating to stories is an indicator of a favorable prognosis. having a name like robojesus is not.

    //k i'm done. I'm not always like this. it's only when I'm awake. sorry
    Not sure where I have ever come off on these forums like I am not happy for someone having a cool or nice car. Why would I be on an Enthusiasts forums talking with other members if that was the case?

    D3 your on a role today not sure what your getting at or where you get your information LOL

    Nice to be singled out though! Geesh I feel special lol

    I meant no disrespect to the OP. Was just seeing where he was at with his problem. Obviously D3 has it covered for you though!

    I am one of the ones that babied the car home and DID pull the tune as soon as I got home and looked at it (maggied V) and it was not a clean tune AT ALL. So yes I ask if he checked this. But I guess we always trust what people tell us.

  16. #15
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    Re: The engine has developed a knock

    the whole thing? I did not see that coming.

    //the more I think about it, the more the MAF delete bugs me. Try... an octane booster additive, one of those $5 bottles from Wal Mart or a parts store. Couple bottles of it, even

    Assuming everything is in the same working order as when you picked it up, the only things that changed are the car's location (altitude, temp, humidity) and the fuel (octane)...

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