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GM ENGINE KNOCK
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Comments
You aren't owed any proof (no need to refute) because the phrase used by your snake oil expert, "essentially the same" is equivocal. Translation: Not the same!
You admitted this to PAman, but for the sake of shame and embarrassment, can't admit to now! Pity!
>While what you claim is true for dino oil, it is not true for synthetic. Both synthetic oils 5W-30 and 10W-30 start with 30W base.<
Where's the proof?
The phrase I refer you to, is that "5W-30 and 10W-30 start with 30W base."
On the contrary, for a multi-grade oil, dino or synthetic, the base stock is the 5W or the 10W number. The second number means the multi-grade oil will not thin more than a single grade of the same temperature.
But the base stock is in the first number. No getting around this.
Thanks.
GMs aren't the only ones knockin !
Interesting reading...............Geo
Bob
But I see you Toy owners over
here bustin' chops.
And the flawless toys have the
same problem !
Just a thought............Geo
I would like to quote something from our book Thermodynamics an engineering approach. Written by Cengek and Boles (last names) 4th edition 2002. Page 460
"The premature ignition of the fuel cell called autoignition produces an audible noise, which is called engine knock. Autoignition in spark-ignition engines cannot be tolerated because it hurts performance and can cause engine damage. The requirement that autoignition not be allowed places an upper limit on the compression ratios that can be used in spark-ignition internal combustion engines."
This really got me thinking. My only questions is why this engine knock (is what we are hearing engine knock?) doesnt hurt performance. No one is complaining of performance being effected
HMMM gonna have to do some research
I would be calmly persistent with your dealer and ask to speak with the district rep. If it was normal they wouldn't have replaced my engine without much of an argument. I guess it really depends also on dealer cooperation.
Ill let you know what i find out
Many people had the "de-carbonizing soak" which cured the knock temporarily. A few have also lost the knock with fuel additives and hard driving. All these facts lead me to believe that it is a carbon issue.
Does anyone have the exact reason or cause?
-Eric
2. Those that have tried to differentiate between the warm engine knock, cold engine knock, and pinging (sometimes called knock) under a load are right---they are three different knocks, caused by three different sets of circumstances. Only one--the knocking or pinging under load--is KNOWN to be dangerous to an engine--so far.
As I have said MANY times in here, the COLD START ticking noise is usually due to a lack of oil or too-thin oil in the top part of the motor at start-up. The fact that the knock goes away on extremely cold mornings seems to confirm the thin oil problem because the petroleum-based oil will thicken considerably under very cold conditions. You can have the knocking due to the piston problem immediately on start-up, but if it goes away, it is a lifter noise, not the piston/ring noise. The piston noise does not go away.
The pinging or knocking under load is caused by pre-ignition, too-far advanced timing, or a fuel with a too-low octane rating, or a combination of all of them. Carbon build-up CAN, but not always WILL cause or worsen pre-ignition knock because the carbon deposits actually get red hot, and ignite the fuel as soon as it enters the combustion chamber, rather than when the spark plug ignites. Pre-ignition can also be caused by a hot spot in the intake or exhaust manifold. This is why engine builders know to polish the inside passages of the intake and exhaust manifolds and the heads--it helps eliminates pre-ignition in a high performance engine.
I hope this helps owners understand that just because you hear a light tapping on a cold engine for a few seconds in the morning, you do NOT have the condition that is causing some to get a new engine or new pistons.
At this point, this condition appears to be either an engineering mistake, or a problem with a supplier providing rings or pistons out of spec.
The GM dealers that tried to do a carbon soak were GUESSING--which is usually a sure sign they don't know what the specific cause or solution is.
If you have a cold-start noise, or a pinging under load, you still need to see a dealer. A cold-start noise in a relatively new engine could indicate a hydraulic valve lifter that is failing or has failed. A pinging under load may mean that the dealer needs to 'flash' your computer, which means they load an updated engine program from a CD-ROM or from GM via telephone. But, neither condition would likely indicate you need to have a new engine.
The few that posted that they had the soak done by the dealer all stated the knocking went away. They stated it came back, after so many miles, but this also points towards a carbon issue.
An oil issue does not appear to be the issue (on mine) and the knock has not gone away with the cold, either.
-Eric
If the noise went away for awhile after a carbon removal process, then all they may have done was caused some of the cleaner to mix with the oil and act as a cushioning agent for the rings--temporarily. By the way, guess what the dealer probably did as part of the soaking process? CHANGED the OIL!! Could be that the fresh additives in new oil helped quiet the engine, or the dealers were adding an oil additive but not telling the owners?? Hmmmmm.....
As for it not starting the noise until it had about a thousand miles, this seems to be consistent with what others are saying--that it was not there when the truck was new, but appeared between 1,000-15,000 miles. Once again, if the rings are pounding up and down in the ring grooves, then that raises concerns many owners have when GM tells them the problem is not causing any wear or durability problems with their engines. A common-sense approach seems to be for owners like yourself to question this when GM tells them it is normal, yet you know it wasn't there when it was new.
Just out of curiosity, have you gone to a higher weight of oil to see if the noise is affected, such as going from a 5W30 to a 10W30 or a 20W50?
Good luck and keep after GM to fix it until YOU are satisfied!
Joe
Combustion in an actual engine is a complex process. It involves processes of evaporation, mixing, turbulence and chemical reaction. It depends also on the compression ratio, air-fuel mixture, amount of charge, charge temperature, octane and cetane numbers of fuel, shape of cylinder and piston, location of ignition source, location of exhaust valve and ignition timing among other variables.
It appears at startup the knocking you briefly hear is due to the rich mixture at startup. The richer mixture (which closer to the correct mixture ratio) needed for the warmup increases the flame speed and ignitability which may result in the short period of knock at startup. I will talk more about this in our next class since it has been of interest to you and some of your classmates. Let us enjoy the long weekend for now! See you next Tuesday.
Does that school you're in have an IC engines course? I did two semesters at senior level. Now I know lots of theory about engines, but can't ID the parts or fix the dang things.
I wanted to buy an Otto cycle, but couldn't find a dealer.
As for mine, it is getting louder now (lasts longer 35-40 seconds), 4K miles, and 25-35 F outside. GM did give me the Major Guard $0 deductible extended warranty, and "the fix" whenever they find it.
At this point I just want to know exactly what is happening/causing the noise, and to what extent is this damaging the motor. Longevity has become a question/concern.
-Eric
I read a few of the analysis results on pickuptruck.com and they all showed high levels of copper, usually indicative of bearing wear... We shall see.
-Eric
Mine too showed high copper content. The report
from the lab states "Copper is left over additive
from the factory fill oil."
Is this the magical ingredient to stop the knock?
If I were in the position of having one of these knocking engines, I would have a copy of the oil analysis in hand each and every time a dealer or GM rep tried to tell me that the noise is normal.
From past experience, I know that the Air Force and major airlines use oil analysis as a leading indicator of premature wear, or major component failure.
If you end up going to the BBB arbitration process, I'm sure the arbitrator would be very interested in the oil analysis from an independent lab....that is the kind of documentation that would easily stand up in a court of law.
rod berings. A combination of elements all reading higher than normal would indicate future failure.
In this case only copper is high. All other components are below average with the exception of the detergent components of the oil.
-- Don
Thanks
Bob
wouldn't we also see a high level of tin? Being that all
of the bearing components are made uo of alloys the
fact that Just the copper is high would indicate that it
is "introduced" into the engine. Mybe as an additive?
Could be. Who knows. We will see on my next two
samples.
http://www.bgprod.com/autofuel.html
Bob
Join us at http://www.gmpistonslap.cjb.net
It's still under construction so bear with me!
Bob
Bottom line... No lifters. No pushrods. Just pretty little clicks that add depth to the total combined music of those engines. If you wanted quiet sedation, you would drive a Mercedez...
Uh.. sorry. I got carried away.. ;-)