2005 STS - V8 knocking
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Cadillac STS Forum - 2005 through 2012 Discussion, 2005 STS - V8 knocking in Past Cadillac Vehicle Discussion; First... hello all. I am new to the forum and a new Cadillac owner as well. I just recently purchased ...
  1. #1
    Raw2005 is offline Cadillac Owners Member
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    2005 STS - V8 knocking

    First... hello all. I am new to the forum and a new Cadillac owner as well. I just recently purchased a 2005 STS with a V8 (car has 95k). Not sure why I didn't notice it when I test drove it before purchasing it but I am hearing knocking that I am unsure about. It is too late to change my mind and take it back so I am stuck with diagnosing and, hopefully, finding the problem. The car runs perfectly (smooth idle and acceleration) and is getting great gas mileage. I noticed today, I don't hear any knocking when it is first started cold. It starts up a minute or so after being started and then fades a bit after the car is warmed up (oil pressure up to norm). At first, I thought it might be a lifter clattering because it sounds a bit like a diesel running (hope that makes sense) but I'm not really sure. I thought I read something about this symptom on the 4.6L NS somewhere but can't find it now.

    It sounds a bit like it is coming from the drivers side (haven't used a hose or a steth yet). I tried adding a bottle of Seafoam to see if that might "unstick" the issue but it didn't seem to have any effect. I only ran it with the Seafoam in it for about 120 miles and then had the oil changed (Mobile 1 - 5w 30).

    Just to restate... it is running great but the knocking has me concerned. Does this symptom ring any bells with anyone here and, if so, any ideas on what I might try that wouldn't involve me selling a kidney to pay for it?

    Really hoping someone has seen this and has some ideas. Outside of this concern, I absolutely LOVE this car and am hoping for a long relationship with it.

    Any help or suggestions would be GREATLY appreciated.

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  3. #2
    1BadCadSTS's Avatar
    1BadCadSTS is offline Cadillac Owners Connoisseur
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    Sounds like VVT chatter. Are you running 91+ octane?

  4. #3
    EChas3's Avatar
    EChas3 is online now Cadillac Owners Master
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    Re: 2005 STS - V8 knocking

    Issues with the 2004 & up XLR/SRX/STS Northstar are very rare but it isn't always a very quiet engine. About the only common issue that since oil pressure is used in the Variable Valve Timing, it is a bit sensitive to oil quality and level, but it doesn't consume oil like the first generation design. Coils do sometimes fail and it runs best with OEM plugs. I doubt there's anything wrong. When do you hear this 'knock'.

    I'd recommend against all oil additives, treatments and flushes, especially snake oil. (Would you like to buy some magic beans?) Use only your choice of GM4718M or better rated oil (my filler cap says Mobil1 5W30), check it frequently at first to be safe and change it when the DIC tells you so.

    Put Top Tier gas in it. Premium if you like, but many members agree it runs fine on most good gas. I run 87 octane with no complaint but sometomes go higher, just to see if there's a difference. Maybe.

    Exercize your N*. It loves regular WOT & compression braking. Read the 'Sticky' at the top of the forum and enjoy. You've bought a great car.

  5. #4
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: 2005 STS - V8 knocking

    My '06 4.6L STS clatters like a '49 Olds with a flat cam. That's one of the reasons they have the plastic side cover panels under the hood. VVT.
    Don't mess with Binky Bear!


  6. #5
    Raw2005 is offline Cadillac Owners Member
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    Re: 2005 STS - V8 knocking

    Quote Originally Posted by 1BadCadSTS View Post
    Sounds like VVT chatter. Are you running 91+ octane?
    Wow... fast responses guys. Thanks!

    I run 91 octane. I did try 89 octane in it but most of what I read seemed to point to sticking with 91+ so I have. The knock sounds a lot like a lifter but maybe just a bit lower in tone (at least the way I remember an old lifter sounding when it didn't pump up). The knock is regular and I really only hear it when I accelerate. At idle, it is essentially imperceptible. I haven't checked for any codes yet (going to do that tomorrow). I was really hoping it might be something simple like replacing knock sensors. I kind of "half tried" a WOT but I was nervous because I don't want to make things worse. Per the dealer and the info pulled on the car, I am the second owner. Not sure what the driving habits were of the couple that owned it before me (believe they were a bit older).

  7. #6
    dkozloski's Avatar
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    Re: 2005 STS - V8 knocking

    Drive it like you stole it.
    Don't mess with Binky Bear!


  8. #7
    Cadillac Cust Svc's Avatar
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    Re: 2005 STS - V8 knocking

    Quote Originally Posted by Raw2005 View Post
    First... hello all. I am new to the forum and a new Cadillac owner as well. I just recently purchased a 2005 STS with a V8 (car has 95k). Not sure why I didn't notice it when I test drove it before purchasing it but I am hearing knocking that I am unsure about. It is too late to change my mind and take it back so I am stuck with diagnosing and, hopefully, finding the problem. The car runs perfectly (smooth idle and acceleration) and is getting great gas mileage. I noticed today, I don't hear any knocking when it is first started cold. It starts up a minute or so after being started and then fades a bit after the car is warmed up (oil pressure up to norm). At first, I thought it might be a lifter clattering because it sounds a bit like a diesel running (hope that makes sense) but I'm not really sure. I thought I read something about this symptom on the 4.6L NS somewhere but can't find it now.

    It sounds a bit like it is coming from the drivers side (haven't used a hose or a steth yet). I tried adding a bottle of Seafoam to see if that might "unstick" the issue but it didn't seem to have any effect. I only ran it with the Seafoam in it for about 120 miles and then had the oil changed (Mobile 1 - 5w 30).

    Just to restate... it is running great but the knocking has me concerned. Does this symptom ring any bells with anyone here and, if so, any ideas on what I might try that wouldn't involve me selling a kidney to pay for it?

    Really hoping someone has seen this and has some ideas. Outside of this concern, I absolutely LOVE this car and am hoping for a long relationship with it.

    Any help or suggestions would be GREATLY appreciated.
    Hello Raw2005,

    Welcome to the forums! I apologize that you are experiencing an issue with your STS knocking. I see that you are reaching out to the community for ideas about what it could be and how you can fix it, but if you are still concerned about the issue, I would like to extend my assistance in working with the dealership. Please private message me if that is something that you are interested in. Please keep us updated about this situation. Thank you for your time.

    Gregory W.
    Cadillac Customer Care

  9. #8
    fredolan is offline Cadillac Owners Member
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    Re: 2005 STS - V8 knocking

    I had the problem with "knocking" whenever I used less than premium fuel (I know, I know, its in my head. . . but it wasnt). I only use 93 octane. This problem was noticed when I first bought the car in 2006 when it had about 40-50k on it. It now has 211k and I just started to hear this knocking again despite the high octane fuel. It is very subtle and most people probably wouldnt notice it. It only "knocks" when there is a very slight pressure placed on the accellerator. In "accelleratio" it does not "knock" at all. I will probably have it looked at and then post what I find. I am hoping to drive this car for another 100k. . . .I hope. It has been an excellent vehicle all around.

  10. #9
    KRSTS is offline Cadillac Owners Enthusiast
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    Re: 2005 STS - V8 knocking

    Knocking rather than pinging? At that many miles I would suspect failing engine bearings

  11. #10
    MurrayP is offline Cadillac Owners Member
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    Re: 2005 STS - V8 knocking

    I've got an 08 STS N* and have had it for 8 months. It is coming up to 100K miles. I was really concerned about the knocking when I bought it with 80K miles. I'm not concerned anymore. The machine is a beast and the worst thing for this engine is to drive it like a little ol' person. Give Her! You'll likely be fine and if she fails on you then you'll be the first one I've read about here in the last 8 months!
    spike1040 likes this.

  12. #11
    EChas3's Avatar
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    Re: 2005 STS - V8 knocking

    I agree with MP.

    I've heard a few of the noises and oddities that get posted. Most times there's nothing really wrong, just condensation here and there or a few air leaks. I've put more than 50k miles on my car and my wife has put almost 70k on hers. She's the leadfoot in the family but usually has a bit in reserve. I like WOT & working gears. It was a kick teaching her the right way to driving long mountain grades.

    These cars always seem to run quieter and perform better after a long hard drive regardless of the gas we are burning or much of anything else. The N* is strong. People who periodically 'warm-up' an underused car for 30-minutes every few months is at best wasting their time and can actually be shortening the life of components because one would have to drive a car very hard to really heat it up & dry it out in 30-minutes; I figure on 2-hours of normal driving or leave it sit. Stainless exhaust sure helps cure that common failing.
    mckellyb and spike1040 like this.

  13. #12
    SRXBob is offline Cadillac Owners Member
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    Re: 2005 STS - V8 knocking

    I have the 2005 SRX with the 4.6 and am the original owner at 96K mi. I really enjoy the car but have just recently noticed what I think is the same noise. With the exception that I hear the noise most when idling. Probably because it's the only time I am outside the car. I would describe it as a "lefter noise" and not a knocking. Hoping this is the same as you described and I can just keep on trucking. I intend to bring it up at the dealer when I go for the 100K mi maintenance. Is there any chance for a 100K mi engine warranty?
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  14. #13
    dkozloski's Avatar
    dkozloski is offline Cadillac Owners 10000+ Posts
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    Re: 2005 STS - V8 knocking

    You have two chances, slim and none.
    Don't mess with Binky Bear!


  15. #14
    EChas3's Avatar
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    Re: 2005 STS - V8 knocking

    If your oil level is reasonable, there's not all that much that goes wrong with the LH2 4.6 V8, other than loose intake manifold bolts. GM even removed fuel filters and intake service from scheduled maintenance in latter years. Members have reported a few troubles but every forum attracts some such. That's a natural bias because not many owners are motivated to report 94,000 trouble-free miles on an engine. (It's kinda sad how engines get retired once they are perfected.)

    There are members that report more upper-end noise than they expect and some are louder than others. My wife's car is louder than mine. She also listens to her music louder. It balances.

    I suppose if it has changed, you could have the timing chain & tensioner checked; cams, too. But having the dealer do so is basically asking for expensive service you car probably doesn't need. Variable Valve Timing uses oil pressure to adjust cam timing. A pushrod motor is quieter, but that doesn't make me want one in my STS.

    Try listening to a GM Direct Injected V8.

  16. #15
    Charles Warren's Avatar
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    Re: 2005 STS - V8 knocking

    I suggest driving it for a long distance. Then do a wide open throttle pass and live happily ever after. I notice my car likes to feel new again when I drive to work on the weekends (overtime and I work 100 miles away from home) instead of riding the vanpool. And I use synthetic oil and even stp Zddp additives, only noises I get are dry belt noises. If a valve is sticking the long distance might seat it or correct it just drive it and you might have a broken engine mount but that's nothing major.

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