: Engine seems to be knocking



Trench
11-09-05, 01:26 PM
My engine recently started to knock.

The car ran just fine until it seems cold weather has arrrived. It does lighten up a little as time goes on, but still stays with me even after the engine has been fully warmed up. I have read up on cleaning with the GM TEC stuff to solve a "cold knock" but I don't think that will apply because it is always there, cold or hot. It does change with throttle. Much worse under hard acceleration. During a slow acceleration it is hardly noticable. Any ideas?

:banghead:

Dustin

Ranger
11-09-05, 02:21 PM
Have you tried some good ole WOT?

Trench
11-09-05, 06:25 PM
Have you tried some good ole WOT?


Yeah, I have. On several occations. Took it on the highway and rode it hard in 2nd gear. Didn't really seem to help anything.

mtflight
11-11-05, 02:58 PM
knocking, ticking, or pinging?

Knocking is not good, obviously. Get a stethoscope for cars (~$10) and with the engine on, try to find it if is coming from the lower end (ramps) or from above (Camshaft). Usually the ticking from the top is normal. You don't hear it while driving with the windows up, do you?

dkozloski
11-11-05, 05:23 PM
If the car is running with the hood up and you are standing there when some one gooses the engine, do you jump back to get away from the flying parts or does it sound like the works are politely conversing with each other? A rod knock will be a very sharp rap that gets much worse with RPM and will really sound off on the over run. It will be obvious that something is trying to break. Most other noises that get gradually louder with RPM and don't change on the over run are probably valve related. The use of a stethoscope as suggested earlier is a very good idea.

Trench
11-12-05, 12:32 AM
The ticking noise, I imagine from the injectors, is only really noticable with the engine cover off.

The engine sound just fine when idling and when be revved up. The knocking seems to come into play under load. Also, the knocking has seem to let up some in the past few days. I will see if I can borrow one of the stethoscopes from work and try to locate it.

keep it fresh
11-28-05, 04:51 AM
my engine knock but i cant hear unless im outside of car and lookin for the sound

auroradude
11-29-05, 12:26 AM
Screw additives, ever tried using Premium Fuel? I always run 93.

Trench
11-29-05, 01:42 AM
Screw additives, ever tried using Premium Fuel? I always run 93.


Screw additives? Blind ignorance is too common these days, almost disgusting. Grow a brain before you post. Also, any response to my comment will be ignored, being as I'm sure I will get one, and I don't wish to start a battle.

Now, are most additives junk, I'm sure most would agree yes.

Are all additives junk? No.

Not to mention, where did that come from? I don't see any mention of additives on this thread. Along with the fact 93 Octane is a waste of money on my year car. The engine is tuned for regular gas. Only benefit of high grade fuel may be detergents.

Honestly...How would high octane fuel help anything in this thread? Our engines are not detonating or pinging.

mcowden
11-29-05, 02:49 PM
My engine recently started to knock.

The car ran just fine until it seems cold weather has arrrived. It does lighten up a little as time goes on, but still stays with me even after the engine has been fully warmed up. I have read up on cleaning with the GM TEC stuff to solve a "cold knock" but I don't think that will apply because it is always there, cold or hot. It does change with throttle. Much worse under hard acceleration. During a slow acceleration it is hardly noticable. Any ideas?

:banghead:

Dustin

Hey Dustin - I have noticed a sound before on my car that might be what you're describing. It sounds almost like there's a tiny diesel engine inside your Northstar. On my car at least, it goes away when the engine heats up. I've also tried lots of WOT (still do it just to be sure) and it never goes away. After much discussion with a guru who used to frequent this forum, I've chalked it up to normal valvetrain clatter. He had suggested using Rotella 15W-40 motor oil for one change cycle to see if the slightly heavier oil would quiet the clatter. I would only do that during the summer months, but I have never tried it. I'm convinced it's nothing to worry about, at least the sound I'm hearing from the front of my car when it's cold. Does yours sound kind of like a quiet diesel sound?

keep it fresh
11-29-05, 05:19 PM
mines has a uiet knock but only noticiable outside of car i was gonna try some slick 50 for heat and friction.....? wat u think the northstar engine does get really hot

Aaron J Williams
11-29-05, 06:03 PM
My 93 Eldo had a light knock when I first got it and I put a half can of sea foam in the oil and put the other half can down the intake then let the car sit shut down for 5 minutes and started it up and drove it till it quit smoking and the sound went away.It still has a cam/valvetrain tick but that sound has never changed and I think its normal. I know some additives are bogus but sea foam has worked for me many times and I use it in anything I have with an engine FWIW:xsmile:

Ranger
11-29-05, 06:22 PM
mines has a uiet knock but only noticiable outside of car i was gonna try some slick 50 for heat and friction.....? wat u think the northstar engine does get really hot
Save your money for something useful. Slick50 is snake oil.

EcSTSatic
11-29-05, 07:12 PM
How many miles on it? I can't hear it obviously, but the symptoms point to rod bearings. Loads put a strain on the crank, heat and expansion diminish the sound by reducing clearance but it won't go away. I've heard that Rotella helps some.

That's my $.02. I hope I'm wrong.

mcowden
12-01-05, 04:10 PM
mines has a uiet knock but only noticiable outside of car i was gonna try some slick 50 for heat and friction.....? wat u think the northstar engine does get really hot

Slick 50 is useless. It won't help friction or temperature. It only helps the finances of the Slick 50 company, not your car.

Trench
12-01-05, 07:22 PM
Hey Dustin - I have noticed a sound before on my car that might be what you're describing. It sounds almost like there's a tiny diesel engine inside your Northstar. On my car at least, it goes away when the engine heats up. I've also tried lots of WOT (still do it just to be sure) and it never goes away. After much discussion with a guru who used to frequent this forum, I've chalked it up to normal valvetrain clatter. He had suggested using Rotella 15W-40 motor oil for one change cycle to see if the slightly heavier oil would quiet the clatter. I would only do that during the summer months, but I have never tried it. I'm convinced it's nothing to worry about, at least the sound I'm hearing from the front of my car when it's cold. Does yours sound kind of like a quiet diesel sound?


That sounds pretty much like my problem. Only it can get pretty bad and only lightens up when warm.

Well, it really started to worry me so I bit the bullet and took it to the dealer. They said the noise is caused by sticky piston rings allowing the piston to wobble around somewhat. They said they have never seen any engine damage to to this. In order to fix it and prevent it from occuring again, It involves redesigned pistons and over $3000 in labor.

Sometimes a decarbonization will help, but I will do that myself sometime soon.

They didn't charge me anything, though. So that was a plus.



Slick 50 is useless. It won't help friction or temperature. It only helps the finances of the Slick 50 company, not your car.

From what I understand that is the perfect truth, nothing more. If anything, it helps for only a few days. But seadfoam and the likes are awesome.

blb
12-02-05, 06:34 PM
The sound you are describing is either cold carbon rap, or piston slap. If you did the Seafoam or GM Top Engine Cleaner service and the noise is still there, it is most likely Piston Slap.

Although Piston Slap is not as prevalent in the Northstar as it is in the LS1, there are more than a few documented cases in Northstars. When the dealer told you about "the piston wobbling around a little bit", he was describing the cause of piston slap. Basically the clearance between the piston diameter and cylinder bore is a little more than it should be, and this allows the piston, which has a relatively short skirt, to rock slightly, causing the noise you are hearing. As the engine warms up, this clearance decreases and the noise will generally disappear, or at least become almost inaudible. Most Chevy dealers will give you an extended engine warranty (up to 8 years / 100,000 miles) if they choose not to tear into the LS1 engine. I have not heard of any Caddy dealers willing to do anything about this in Northstars unless the customer is willing to pay.

To learn more about the GM Piston Slap issues go to:
www.pistonslap.com

Trench
12-04-05, 02:40 PM
I did try the Top engine cleaner. What you said seems to pretty much be what I have. unforutnatly.

mcowden
12-04-05, 04:56 PM
I did try the Top engine cleaner. What you said seems to pretty much be what I have. unforutnatly.

I have noticed the same thing on my car. It hasn't changed in 62,xxx miles, so I'm not worried about it. I give it lots of WOT and have also done the TEC stuff and it makes no difference. The sound is so quiet, though, I don't always notice it and when I do, I just ignore it. Obviously it's not getting worse and the engine runs fine so I don't worry.

Trench
12-04-05, 04:58 PM
I have noticed the same thing on my car. It hasn't changed in 62,xxx miles, so I'm not worried about it. I give it lots of WOT and have also done the TEC stuff and it makes no difference. The sound is so quiet, though, I don't always notice it and when I do, I just ignore it. Obviously it's not getting worse and the engine runs fine so I don't worry.


Mine can sound aweful as all hell when cold. Usually it lightens up when the engine warms up. Usually I can still hear it pretty well. Sometimes it seems to go away, though. It just sounds like crap.

Ain't I pimpin'

blb
12-05-05, 11:18 AM
If you are using synthetic oil now, try switching to conventional oil for one oil change interval. I know that more than a few LS1 owners have reported the piston slap disappearing after switching to conventional oil. This is because since the viscosity of conventional is higher when the oil is cold, the thicker oil actualy helps cushion the rocking piston against the cylinder wall. When everything heats up and the viscosity of the oil is lower, by that time the excessive clearance between the piston and cylinder has been reduced due to thermal expansion and the noise no longer exists. By contrast, the viscosity of synthetic oil remains more consistent over a wide temperature range as compared to conventional oil, so you don't get as much of the effect of higher viscosity at lower temperatures with synthetic.

EcSTSatic
12-05-05, 11:27 AM
... Much worse under hard acceleration. During a slow acceleration it is hardly noticable. Any ideas? Dustin

There is an engine load factor in the symptoms. I may be wrong but this just doesn't sound like piston slap to me. Slap will usually occur until expansion improves the clearance problem. As blb mentioned, slap should go away after driving a while. This doesn't read that way.
I think it's something else, although I have read some 3rd party Northstar evaluations that said carbon issues sound like bearing knock.

blb
12-05-05, 01:28 PM
You're right EcSTSatic. If its piston slap, it shouldn't be worse under acceleration. There must be something else going on here.

Trench
12-05-05, 09:09 PM
You're right EcSTSatic. If its piston slap, it shouldn't be worse under acceleration. There must be something else going on here.


What else do you think it could be? there are times that is goes away completely, though. So it is not always there, just usually. Onces the engine is warmed up, it is by far better. This issue also seemed to start up when the temperature dropped beloew 50 degrees.

It also has regular Dino oil in it. Motorcraft specifically since it was purchased from a ford dealership.

EcSTSatic
12-05-05, 11:38 PM
You never answered with how many miles the engine has on it. If the engine is worn out, expect bearings. If it's newer it could be stuck rings I guess. A gas/oil treatment like marvel Mystery Oil might help.

Since we can't hear or test drive it, I suggest you get a few local opinions on where the sound is coming from.

mtflight
12-05-05, 11:42 PM
Since we can't hear or test drive it, I suggest you get a few local opinions on where the sound is coming from.

Cadillac dealership may provide a good estimate for like $50.

Trench
12-06-05, 09:05 PM
The car only has 51,000 miles on it. I had my local dealer check it out, free of charge, and they said it was stuck piston rings. But appearently some of you disagree. Bah


for that simple fact I will probably take it in shortly to a local shop I can trust..if there is one.

boricuacaddy
12-08-05, 09:31 AM
Well, I have not started my car for about a Month, it has been sitting in my garage covered up. Yesterday in the morning I decided to use it and started it up, it sounded awful the knocking was very loud:eek: ! It was like 0 degrees in the morning. I was shocked to hear the knocking, it has never done that before. I have 65000 miles and have it maintenanced regularly, I just had changed the oil before I parked in the garage. When I heard the knocking I shut the car off immediatly and restarted it and it still was knocking loud, I let it run longer and it quieted a little as it warmed up but I still could hear it from inside the car. I drove it as is and did a WOT on my way to work and the tick went away. After work I was worried it would do it again when I started, especially since my coworkers were around. It would be very embarrassing starting my car up and hearing the Awful knocking coming from my precious Caddy :crying2: and all my coworkers hearing it too!:hide: I was happy when it didn't knock. The burning oil thing I could live with but the knocking I defanatly can do without! :alchi:
David

Ranger
12-08-05, 11:38 AM
What you are expiriencing is "cold carbon rap". A good dose of WOT is all she needs. I noticed my '97 Deville was more prone to it after setting for several days rather than daily use. Can't explain why but, nothing to be concerend about.

boricuacaddy
12-08-05, 02:48 PM
Thanks Ranger! I will defenatly open her up more often, I am not use to doing WOT! It is hard to do, since I live in the city too much darn traffic. I will have to get up early in the mornings or late at night and get on the highway and let her rip! It will be well worth it to keep the knocking on the down low!

David

59cadillac
12-08-05, 05:40 PM
Thanks Ranger! I will defenatly open her up more often, I am not use to doing WOT! It is hard to do, since I live in the city too much darn traffic. I will have to get up early in the mornings or late at night and get on the highway and let her rip! It will be well worth it to keep the knocking on the down low!

David

I have the same problem with my 97 Deville. The knocks come and go. I even took it to the dealer and they cleaned the throtle body, which did not help. They also couln't figure out what was cause this knock. So I drove it anyways. I figure when it breaks down, then I'll know. One day I was replacing a small piece of coolant hose under the throttle body when I put a small hole in the aluminum tube (EGR) I started the car, but didn't drive it, and the knock soon was heard (very loud the next day). When I replaced the tube, the knock went away and I havent heard it since. So I think this has to do with the EGR system, emissions. hope this info helps.