: WOT's northstar knock?



thydarkprevails
11-10-06, 03:53 PM
i just got done doing 2 wot's and now i'm hearing a persistant knocking on acceleration...is that the famous northstar knock i've heard so much about. i'm sort of afraid to do anymore and possibly damage my engine if it's not..any advice?

thydarkprevails
11-10-06, 04:01 PM
i should mention that prior to doing wot's i had no knock...and now i have a knock after performing them, also there is no noticable knocking in idle, just accelleration

GreenMachine
11-10-06, 05:00 PM
the "knock" northstars are known for is during warmup when the engines cold. What could have happened (if you haven't done any work on the plugs) is that the gap on the plug has opened up, possibly from the platinum tip coming off....not sure if that would cause a knock, might misfire.

Are you using premium fuel (rated at 91 octane or higher) ifmay be that once you had your engine up into the higher limits of operating temp you were getting a little pre-ignition or post-ignition explosion (my terms might be off a bit)

I'm sure someone will have an idea for ya.

thydarkprevails
11-10-06, 05:07 PM
i just replaced with the oem ac/delco plugs 600 miles ago, and i've only put 93 octane in the vehicle.

i need to go somewhere tonite, so i'm gonna drive it anyway, i did notice that the knock didn't start till i came to a stop sign after the wot's. and it seems to go away after i get to 20-25 mph or so

thydarkprevails
11-10-06, 05:19 PM
upon further inspection i guess it is noticable at idle, but only when the hood is up..

fpmesiIII
11-10-06, 08:10 PM
could be bad fuel.

codewize
11-10-06, 11:31 PM
Octane doesn't matter here. The N* has a very high tech knock sensing system that can overcome almost any pre-igniotion.

If it didn't do it before and it does it now, I'd pull the plugs out and take a look.

Mine knocks until it's up to temp then it's quiet as a mouse. If the knock is there even after it's warmed up I'd stating investigating.

NOTE: the infamous knock is due to carbon build up in a special part of the combustion chamber called the vortex chamber, or something. When it gets buildup in it the piston hits it which is why we call it piston rap.

I think that's correct. ANyway, look here for a little more info
http://www.cadillacforums.com/forums/cadillac-tech-tips/51792-cleaning-your-engine-evil-carbon.html

nigelb
11-11-06, 04:12 AM
if the noise started after doing some WOT's maybe an oil change could help.
you might have a sticky lifter or some crud in a camshaft oil passage.
often these noises do come and go almost by magic.

eldorado1
11-11-06, 08:34 PM
Octane doesn't matter here. The N* has a very high tech knock sensing system that can overcome almost any pre-igniotion.


Detonation, not preignition. Detonation makes noise that can be detected, preignition doesn't.

Actually it's a low tech knock sensing system... nothing more than a microphone to listen for a certain ringing.

How soon after the WOT's did the knocking start? How does it run otherwise? I would be a little nervous at this point, assuming you know what knocking sounds like, and aren't confusing it with a lifter ticking or something like that. You don't have any codes, do you? There could be an ignition timing problem. I would probably just take it in to a dealer that's familiar with northstar quirks and get it diagnosed. They can run some TEC through the engine and/or let it soak in the cylinders to remove all the carbon. If it still knocks after that, you know you have a serious problem.

chazglenn3
11-11-06, 09:10 PM
I was thinking the same thing...my engine woes started shortly after some WOT runs. Not that the runs caused the problem, but the problem surfaced shortly afterward. Should have my car back by the end of the week complete with a new remanufactured Northstar!

codewize
11-11-06, 11:22 PM
Right, detonation. I guess I meant hi-tech in the sense that it's good at what it does and is very sensitive to the issue at hand. :)



Detonation, not preignition. Detonation makes noise that can be detected, preignition doesn't.

Actually it's a low tech knock sensing system... nothing more than a microphone to listen for a certain ringing.

How soon after the WOT's did the knocking start? How does it run otherwise? I would be a little nervous at this point, assuming you know what knocking sounds like, and aren't confusing it with a lifter ticking or something like that. You don't have any codes, do you? There could be an ignition timing problem. I would probably just take it in to a dealer that's familiar with northstar quirks and get it diagnosed. They can run some TEC through the engine and/or let it soak in the cylinders to remove all the carbon. If it still knocks after that, you know you have a serious problem.

thydarkprevails
11-11-06, 11:50 PM
ok, well i was out all day and could not read these posts, but here are some particulars.

the knock was first noticed after i came to a stop sign roughly a mile after doing wot's. i accellerated on the sign and noticed the knock..i also notice that the knock definately is NOT there at idle, but when i gas it a bit, it does start...more so in drive than in park, but it is still there in park. also the knock seems to come up real quick...maybe knock for 4 seconds, go away, than knock again..it's very intermitant but is definately knocking. it sounds like it's coming from the cylinders on the drivers side of the engine. the knock is also noticable, but it is not loud, it's not like i threw a rod or anything. i did run my codes, and i have absolutely no problems there, i have one body code but that is an unrelated, pre-existing matter with a passenger side mirror. i have drived around 30 miles since the knocking, and do not notice any problems whatsoever, the car drives fine, and still accellerates great, so that, and the lack of codes makes me want to rule out a misfire, or any spark plug issues, but i will check to be certian. plus my SES is not illuminated.

i have noticed since the wot's that i have a bit less smoke as the car warms up at startup, and the knocking is definately more noticable on a cold start...so i'm really thinking i may just have some carbon in there that needs to be cleared out, at least i hope so. i am going to change the oil coming up soon, and see of that is a cause, but i've only put 2k on this oil, and it looks like it's in good condition as well.

thanks for all of your input

codewize
11-11-06, 11:55 PM
If I had to take a guess into the mechanical realm I would say wrist pin.

But it still could be carbon or a blocked oil passage.

thydarkprevails
11-12-06, 12:37 AM
i'm going to change the oil and try some wot's again..if it gets worse..... you might see me on the news robbing a bank to fix the car ;)

dkozloski
11-12-06, 12:58 AM
i'm going to change the oil and try some wot's again..if it gets worse..... you might see me on the news robbing a bank to fix the car ;)
You're in the right place for it. Joliet?

thydarkprevails
11-12-06, 01:06 AM
hahah yep....ya gotta love a town known for it's prisons and godawful smell lol

chazglenn3
11-12-06, 01:06 AM
Blocked oil passage...yeah that's what I had alright. The entire oil pickup screen was blocked! (Chunks of silicone from a botched oil pan reseal job) :mad2:

thydarkprevails
11-12-06, 01:29 AM
ohh..how did you rectify that problem..was it easy to do in your driveway, as that is probably what i will do.

nigelb
11-12-06, 03:39 AM
unfortunately for chaz things were not that simple, when you rob that bank he may want to come with you.

dp102288
11-12-06, 08:27 AM
^^ :histeric: Robbing a bacnk to fix your Caddy, I never though it would be this bad.

Weird thing about the knock. I have done that in my car (ESC) and the SLS lots, and never gave it a second thought.

thydarkprevails
11-12-06, 11:03 AM
well i think the first thing i'm going to do is more WOT's, unless anyone here can strongly advise me against it......

chazglenn3
11-12-06, 07:36 PM
ohh..how did you rectify that problem..was it easy to do in your driveway, as that is probably what i will do.

I bought a remanufactured Northstar for $2800.

blb
11-13-06, 10:18 AM
This reminds me of a thread a while back where our resident expert advised plenty of WOT's and a guy developed a knock. The next WOT resulted in a rod through the side of the block.

Anyway, check simple things first like loose torque converter bolts. They will give symptoms like you are describing.

krimson_cardnal
11-13-06, 10:33 AM
If I had to take a guess into the mechanical realm I would say wrist pin.

But it still could be carbon or a blocked oil passage.

Wrist Pin_??

krimson_cardnal
11-13-06, 10:43 AM
Here's a re-fresher article: http://www.cadillacforums.com/forums/northstar-performance-technical-discussion/80036-detonation-pre-ignition.html?highlight=detonation
Good Stuff K_C


Detonation, not preignition. Detonation makes noise that can be detected, preignition doesn't.

Actually it's a low tech knock sensing system... nothing more than a microphone to listen for a certain ringing.

How soon after the WOT's did the knocking start? How does it run otherwise? I would be a little nervous at this point, assuming you know what knocking sounds like, and aren't confusing it with a lifter ticking or something like that. You don't have any codes, do you? There could be an ignition timing problem. I would probably just take it in to a dealer that's familiar with northstar quirks and get it diagnosed. They can run some TEC through the engine and/or let it soak in the cylinders to remove all the carbon. If it still knocks after that, you know you have a serious problem.

thydarkprevails
11-13-06, 03:51 PM
here's an update...i passed someone @ 5200 rpm today going around 60 or 70. my car sat for 8 hrs and i drove her home. the knock was noticable for 1 second upon ignition, and the same during accelleration, maybe 3 seconds than. now it is not noticable at idle, and is at accelleration with the engine at normal operating temperature. however, it is only really noticable upon hard accelleration in all speeds, and lighter accelleration up too 30 mph or so...

i'm kind of hoping it's getting better, but i'm just not sure.

Ranger
11-13-06, 04:41 PM
I have never heard of this being caused by WOT. I remember the incident that blb speaks of, but that was a freak and I suspect it was going to happen eventually, WOT or not. I suspect that maybe you just have a bad case of carbon build up.

thydarkprevails
11-13-06, 04:44 PM
that's kind of what i was hoping too ranger...especially since after passing that guy @ 5200..the knock is a bit less prevolent..i'm thinking i may have cleared out some of the carbon when i did that, and maybe a couple more WOT's would even help...

also, remember that excessive exhaust i told you about? it is still there, but not as excessive as before, and does not go on for 10 minutes like it used too, only 3-4...that sounds like carbon to me as well

codewize
11-13-06, 05:37 PM
Unless the N* uses some other fancy system, the wrist pin holds the piston to the connecting rod. The initial description of this problem sounded like that but since it's changing I'm not so sure.

Wrist pin knock will sound like a rod knock and is usually more noticeable on acceleration and deceleration. They don't get better, they get worse quick.

I had a small block Chevy that I did this to. I raced a guy and the next day had a small knock. Ran the car around for a day or 2 trying to figure out what it was then one day I was sitting with the car idling and she let go. Connecting rod through the side of the block. Not fun on an original 327 in a 67 rag-top Camaro



Wrist Pin_??

eldorado1
11-13-06, 06:28 PM
The most likely failure mode is a rod bolt loosening, causing a catastrophic rod failure. This seems to happen...mmm... a lot. (or at least too often) Happened to my 2000. Punched a hole in the block under the intake. Heard of a couple more cases happening on here...

This will be indistinguishable from a carbon rap. The only way to eliminate it is to pour some TEC into the engine, and see if it fixes it. If not, you're in for an engine overhaul. TEC will remove any carbon from your engine. So if you're still knocking afterwards you'll know why.

thydarkprevails
11-13-06, 09:24 PM
it's definately not wrist pin knock...there is no noise on deceleration...just when i give it more gas really...and the noise has been so wierd..i just came back from a 30 mile round trip and you can only hear it for literally 1/2 on cold start..than when you hit the pedal hard it goes for maybe 3 seconds, absolute tops..there is no loss of power or driveability issues..

also the noise is WAY too quiet to be a rod or anything...but i'm now worried about that rod bolt lol


kind of really sucks having only one car as a daily driver

dp102288
11-14-06, 08:22 AM
I second the TEC treatment. If doubt about carbon still in the engine is present, then TEC will proves whether or not you are having other problems.

thydarkprevails
11-14-06, 03:11 PM
well, i'm one of the unlucky ones

i was on my way to work this morning, with full intentions of doing the TEC after i got home, but i only have one car, so i had to drive it....about 5 miles away from my shop i threw a rod right through the side of the engine block....

time to find a reputable remanufactured engine company

clarkz71
11-14-06, 03:22 PM
That's a drag, sorry to hear it.

thydarkprevails
11-14-06, 03:37 PM
yeah thanks, it wouldn't bother me so much, but i'm still 6 grand in the hole on the car, and there is no warranty whatsoever on it...so i'd hate to sell it to a salvage yard or something, take the loss, and get a new car...i'm strongly considering the 5k for a jasper

Ranger
11-14-06, 04:29 PM
OMG! Sorry to hear that. I would not blame it on the WOT though. That may have speed up the inevitable, but my guesss is that it was going to happen anyway. You are definately unlucky. This is only the second time I have heard of this. I would think that even the dealers don't see this very often.

eldorado1
11-14-06, 04:42 PM
Damn, can I call it? j/k... Sorry to hear about your luck. If you don't have the money, there are plenty of used engines out there waiting for homes...

I beg you though - PLEASE do an autopsy on it. I can probably find someone local to you who will disassemble it for free and find out what happened... My guess is one rod bolt loosened and caused the other one to loosen and shear...

thydarkprevails
11-14-06, 04:48 PM
yep..my buddy actually was so interested he took his lunch break off to look at it in more depth...seems like a wrist pin broke, causing a nice chain reaction

eldorado1
11-14-06, 04:49 PM
Pics?

Is the rod still attached and whole?

thydarkprevails
11-14-06, 04:59 PM
i will see if i can get some pics, and the rod actually cracked right in too, a piece a little less than an inch was sticking in the block, with a smaller whole on the outside of the block

AlBundy
11-14-06, 05:11 PM
Yes please post pics.

eldorado1
11-14-06, 05:21 PM
If the bottom half of the rod is still attached to the crank, you can probably rule out rod bolts.

codewize
11-14-06, 09:42 PM
HOW MANY MILES ARE ON THAT?

I do believe I said something about a wrist pin?

Anyway I'm sorry to hear about that but I did say that a wrist pin knock will only last about 2 days didn't I. I think I'm going to buy an extended warranty. I would be in big trouble if that happened to me, as I'm sure you are.

I would start scavenging for a short-block.

chazglenn3
11-14-06, 09:46 PM
Try these guys. I got my car back today, and the engine runs great!

http://cgi.ebay.com/ebaymotors/95-97-Remanufactured-Cadillac-Northstar-Engine-Y-or-9_W0QQcmdZViewItemQQcategoryZ33615QQihZ003QQitemZ1 30047232926QQrdZ1QQsspagenameZWDVW

thydarkprevails
11-14-06, 10:02 PM
HOW MANY MILES ARE ON THAT?

I do believe I said something about a wrist pin?

Anyway I'm sorry to hear about that but I did say that a wrist pin knock will only last about 2 days didn't I. I think I'm going to buy an extended warranty. I would be in big trouble if that happened to me, as I'm sure you are.

I would start scavenging for a short-block.

you had it man, i was hoping carbon..but dammit ya had to be right lol


btw 93240 miles


very very sad

and chaz, i'll check into that, thanks man!

thydarkprevails
11-14-06, 10:20 PM
hey chaz, they look pretty good, the only thing that worries me is name recognition. i mean, with jasper, you know that 40k miles later, it's still gonna run great...i'm just not positive on these guys till i do more research

chazglenn3
11-14-06, 11:16 PM
These guys have been around a while, and haven't had any engines come back. They also build very high performance Northstars. I'm sure the warranty is as good as Jasper offers. I looked at Jasper, but couldn't understand why I should pay $5500 for their motor when I could get one for $2695 with a 3 yr/unlimited mile warranty. Give them a call tomorrow and talk to Dave...he will answer any questions you may have. I had to call and talk with him before I decided to order.

dp102288
11-15-06, 08:14 AM
Man, so sorry for your problems. I know the feeling, you get a car, hope its a dream, but every week its something else. Whatever you decide to do, keep or sell, good luck. What a shame. :(

codewize
11-15-06, 08:39 AM
Believe me I didn't want to be right. That is sad on a 93k engine. Something just the way you very first described the sound reminded me of my incident.

Best of luck with that.


you had it man, i was hoping carbon..but dammit ya had to be right lol


btw 93240 miles


very very sad

and chaz, i'll check into that, thanks man!

VinnyT
11-19-06, 08:57 AM
Sorry to hear that Thy. However, I have read all the posts on this thread and to me I think there is a distinctive difference between a rod knock and detonation. Detonation is the sound of shaking an empty spray paint can and rod knock is deeper like someone knocking on a desk or a door. Also for the noise to go away after a few seconds is strange, especially if it was a wrist pin. Normally a rod knock will be heard throughout the whole rpm range. Hope you get her fixed and it works out for you.

V.

GreenMachine
11-20-06, 07:48 AM
very sad news. Makes you wonder what the past owners possibly neglected. What usually causes a rod to be throw can be something as simple as forgetting to change the oil for an extended amount time and running it well below what it should be it.

Real shame.

blb
11-20-06, 10:09 AM
This reminds me of a thread a while back where our resident expert advised plenty of WOT's and a guy developed a knock. The next WOT resulted in a rod through the side of the block.

Sorry to hear this, but if misery loves company, you're not the first, and unfortunately probably not going to be the last.

Dooman
11-20-06, 11:14 AM
I'm not a fan of the WOT for 'maintenance'. Not on a used car that we have no real history of. I run mine up to speed but lately I'm just happy it runs strong, two years after my headgasket repair. I will never again do the drill on a highway up and down to redline, no way..

GreenMachine
11-20-06, 01:20 PM
I always felt doing it more than once or twice wasn't really needed, 5 the max, getting into double digits and weekly a little much, thats just an opinion though. just a quick run from 1st to the top of second is good enough to clean it out I would think, but transmission braking over and over and over could put added strain...with that said it only sped up the inevitable, at some point in that engines life it was abused most likely.

By abuse I mean poorly maintained, crap gas, etc like I said above. With a new engine and proper break in, drive that SOB like you stole it during warranty so that you can validate and test out the repairs and so that if another catastrophic failure were to occur it would be warranty work.

eldorado1
11-20-06, 01:40 PM
Still waiting for pics

Ranger
11-20-06, 04:25 PM
I always felt doing it more than once or twice wasn't really needed, 5 the max, getting into double digits and weekly a little much, thats just an opinion though. just a quick run from 1st to the top of second is good enough to clean it out I would think, but transmission braking over and over and over could put added strain...with that said it only sped up the inevitable, at some point in that engines life it was abused most likely.

By abuse I mean poorly maintained, crap gas, etc like I said above. With a new engine and proper break in, drive that SOB like you stole it during warranty so that you can validate and test out the repairs and so that if another catastrophic failure were to occur it would be warranty work.
"Crap gas" (whatever that is) would never cause a rod to be thrown.

GreenMachine
11-20-06, 09:24 PM
"Crap gas" (whatever that is) would never cause a rod to be thrown.
I figured it could be anything, you get that thing knocking and detonating, igniting for prolonged periods, you'll cause some damage. The main thing is that I think there is an untold story to this car prior to its current owner getting it is all :P

Ranger
11-20-06, 09:46 PM
Well, remember it has a knock sensor so it should not have been knocking or pinging, but I agree that there was probably an untold story. Perhaps there was previous work done and the rod bearing cap was not torqued properly.

eldorado1
11-21-06, 11:48 AM
.......or the rod bolt(s) loosened from the factory... lacking pics or a better description it's hard to tell what happened.

thydarkprevails
11-22-06, 04:53 PM
update

i wasn't able to get pics of it, and the car is now gone. i am happy though, i was offered 4,500 for it in present condition by a local buyer, so i took the money and ran. now i am just on the search for a new car. i love caddy but i just cant afford the maitnence at this point in my life, even the parts alone are too much for me. 12 bucks an hour really doesn't get you very far when you're 28 grand in debt and have other bills to pay. i think i'm going back to my old standby, and getting a thunderbird, definataley a 4.6, though i am sure it is blasphemy on these boards, ya gotta do what ya gotta do.

but, in a few years, i will be exactly where i want, and brand new sts here i come :)

i really would like to thank everyone on this board for their help and support though, ranger in particular, your help has really been appreciated...

thanks guys...hope to see you again in a couple years :)

Ranger
11-22-06, 05:00 PM
Sorry to see you leave the Cadillac family. I'm sure Ford has their problems too. You had a stoke of bad luck. I would bet if you did some searching and found the right car, you'd probably not have this problem again, but like you said, ya gotta do what ya gotta do.
Best of luck to you.

dp102288
11-22-06, 09:40 PM
Good luck. Feel free to come back if you decide to leave the board.

chazglenn3
11-22-06, 11:57 PM
Yeah, all makes have their issues. I owned a '94 Lincoln Mark VIII a couple of years ago, seemed like I was always fixing something, and parts weren't any cheaper for that car either.

thydarkprevails
11-25-06, 10:58 PM
yes, well i have found my 96 tbird lx, and i'm not saying ford is superior in any way....i'm still a cadillac man in my heart, always will be...and i'll still be lurking and posting general questions on these boards....i'm just going to wait till i get a bit more money saved, and a few years under my belt, so i can get that caddy with low miles, and a much more, unguessable history...that way i know what i'm getting into :)