: 2005 STS - V8 knocking



Raw2005
06-12-13, 11:10 PM
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.

1BadCadSTS
06-12-13, 11:28 PM
Sounds like VVT chatter. Are you running 91+ octane?

EChas3
06-12-13, 11:58 PM
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.

dkozloski
06-13-13, 12:17 AM
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.

Raw2005
06-13-13, 01:23 AM
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).

dkozloski
06-13-13, 02:27 AM
Drive it like you stole it.

Cadillac Cust Svc
06-14-13, 06:14 PM
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

fredolan
12-18-13, 08:30 AM
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.

KRSTS
12-18-13, 09:09 AM
Knocking rather than pinging? At that many miles I would suspect failing engine bearings

MurrayP
12-18-13, 09:16 PM
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!

EChas3
12-19-13, 04:49 AM
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.