GM ENGINE KNOCK

ryanbab

this is great entertainment bama

modvptnl

N/M

ndahi12

Please post some pictures of the different oils. This way we can all believe you. After all a picture is worth a thousand words :-P

quadrunner500

Please ask your "expert" (LOL!) to explain how a 30W base stock, (which you've already admitted is a cold flow rating), can behave as a 5W or 10W at the same temperature? Mobil 1 must be using viscosity degraders? to thin the oil out? ROFLMAO

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!

jmsintx

This is exactly why synthetics do not need the the same quantity of VI improver additives ( note the term quantity ) that dino oils require. Synthetics start out with a baseline viscosity, based on the uniform molecular weight of the polymer. By altering the molecular weight of the polymer for a given viscosity, you can change the cold flow point and flash point, while maintaining the viscosity. 5/30 and 10/30 really are the same oil, given the levels of accuracy of measurement in the testing equipment, if you can get +/- 5% that is very accurate. Example : Car manufacturers will hold back engines that dyno out in the top 10% or so of horsepower, compared to the other production engines, and use those top 10% of engines in " special edition" engines or IROC cars. Oil is the same way, batches of engine oil produced will yield characteristics that will follow a Bell Curve.

modvptnl

Everything was making sense until your goofy example.

quadrunner500

You made the following assertion:

>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?

quadrunner500

You said Bama is "precisely correct." Care to parse out where?

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.

quadrunner500

I can read. But can you remember? Because that's the second time you've cited the paragraph saying 5W-30 and 10W-30 are the same oil, but refuting yourself to PAman that they are different in #261.

PAman

....could we get back to discussing the GM engine knock question before the moderator shuts this forum down?

Thanks.

sonjaab

Take a trip over to www.tundrasolutions.com
GMs aren't the only ones knockin !
Interesting reading...............Geo

4x4man

Well, thought this was never gonna happen, but my wife's new car has the knock (just turned 800 miles). Sounds worse than my 8.1L did when it was knocking. Way to go GM...add the 1.9 to the list of engines that knock. Goes to the dealer next week as the service manager stated it wasn't normal. Of course once I get to the dealer they will probably have already been told this is normal and to blow us off..who knows, we shall see. Grrr...

Bob

whatsachevy

If anyone is that concerned about the engine knock, why don't you call GM Customer Service at 1-800-222-1020. They will give you a FREE 5-year/100,000 mile warranty on the engine and all internal engine components. Also, when the newly engineered pistons are available, they will replace your existing pistons FREE if you so choose, and you still have a FREE 5-year/100,000 mile warranty on the engine. Although I'm not that excited about someone tearing into my engine, and I don't plan on having that done based upon how many gasoline engines have a cold start-up knock (some with many miles and no oil consumption), what have you got to lose by calling? At least GM is standing behind their product. Has Toyota offered a similar deal for thumping Tundra engines?

sonjaab

Not to start any trouble here.
But I see you Toy owners over
here bustin' chops.
And the flawless toys have the
same problem !
Just a thought............Geo

ryanbab

Today I actually learned something

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

smith53

i think the knock you learned about today is also called spark knock. it is more commonly heard while accelerating or under load. it tends to sound more like a rattle than a knock.(i think this is correct maybe not)

ricsch

a few days ago about this engine knock on start up, told them I had called the dealer, who faxed me a memo from GM stating it is a normal condition and the like. I told the rep that I believe it is not normal as others have had pistons, and engines replaced because of it, and as I plan to keep the vehicle for several years, I would like to see this issue resolved. Of course they asked if I had a dealer check it out, which the purchasing dealership claims from GM that it is "normal", so I plan to take it to another dealer, BUT, this morning, with the truck sitting outside in 10 degree weather, the noise wasn't present. So, would this mean I don't have the infamous cold start knock? At warmer temps. there is a noticable knock on start-up.

edetor

I also had the cold start knock before they replaced my engine but I also didn't hear it when it was extremely cold out because the engine was revving up to get to operating temp. Either it wasn't there because the engine was not at idle or the added noise due to the engine revving drowned the noise out.
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.

ryanbab

Well if it was then the silverado isnt experiencing an actual engine knock people are just associating that because it sounds like a knock? I emailed chevy and im going to talk more in depth with my professor because i am really curious. Im no expert on this i have an occasional start up knock. It happens once in awhile. I havent heard it in over a wk but then again i may hear it today

Ill let you know what i find out

eric2001

If this start-up knock is really just a carbon buildup as originally claimed by GM.

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

PAman

1. First of all, I drove a BRAND NEW 2001 GMC Denali a couple of weeks ago, and the engine had the knock. You can't have a carbon build-up on a new engine.

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.

eric2001

I disagree with you. Mine did not start knocking until after 1000 miles. The weather/temperature was no different from day one until it started knocking.

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

PAman

If your knock does not go away when it is cold, then it is not a lifter noise--it is the piston or ring noise--just what I said.

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

ryanbab

Ryan,
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.

michgndr

That's it. Bad knock is all autoignition.

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.

ryanbab

dont think that they do. This is the first class which we are actually learning something which i feel is useful. Wish they did have automotive classes id be first in line

eric2001

No, haven't tried a higher weight, may do so in the summer. Its too cold to swap in a heavier oil. If it is a wear/oil issue, why do synthetics not help?

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

obyone

Did you ever have your oil analyzed? I did and mine showed a high level of copper. So what does that mean? Not sure yet as will do another analysis in 3000 miles.

eric2001

Not yet, changed it at 800 then let dealer do the free change @ 3100. When I change it in another 1000 I will send in the kit. BTW I got the free kit in the mail, just have to use it.

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

gator36

I had the Blackstone Labs oil analysis done.
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?

PAman

Copper is one of the metals used in MAIN BEARINGS....

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.

gator36

That copper is not the only element of the main and
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.

obyone

When the lab did my first analysis, they stated that the high level of copper was probably from an additive in the oil. They then requested a sample of the lubriplate as they had no unused oil to compare against. So....I send them a sample of virgin lubriplate, they did another analysis on the unused oil which showed NO copper. So they change their diagnoses to say that copper is usually from poor wearing brass and/or bronze parts. Hmmm...could have sworn we were talking copper and not brass or bronze. They go on to say that it can also come from sealers and after market oil additives. Hmmm...nope haven't used any of that. BTW, my reading on copper was 64. I don't have any knock, ping, or knock on cold start up. I also show double the norm of calcium at 2757.

minikin

analyses on my Hondas cite high levels of copper which they suggest may be left over from previous oils even tho these engines have been run on Mobil-1 for their entire lives except for the first few thousand when brand new. At the same time, they note the engines are wearing well. Especially considering the previous posts, I think their base reference may be flawed. Haven't sent them a sample from my truck yet, but will at the next oil change @ 15K miles.
-- Don

joe3891

If the copper is from the main or rod bearings thats big trouble,next is engine failure.

ricsch

how would I get a kit to send in engine oil for analysis? What is the cost of the testing?
Thanks

ryanbab

go to blackstones labs site and they will send you a free kit. I think the cost is like $15. Ill probably send one in for the heck of it this spring i have a kit sitting here

4x4man

Well, decided that I am first going to put in some BG-44K into the new Saturn to see if that takes care of the knock. Hey it worked on my 8.1L....fingers crossed...

Bob

obyone

is that something like Marvel Mystery oil?

sfish

in a hot engine. Worse with increased ambient temperature or load (towing). I stille have a 91 Explorer that had a bad ping in similar situations started at 17 K and lasted for 120K miles. I did everything, changed the computer, etc. only fix to burn premium unleaded which I refused to on a philosophical basis. Engine now at 164K, no pinging, and doing great. I am not sure mild pinging is always bad. I hope it isn't 'cause my '01 Rado has the cold knock + hot ping.

joe3891

When i read they changed the clearances on the 01 that puzzled me.That is initially set when the engineering design team spec the engine.

gator36

If the high level of copper was due to main or rod bearings,
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.

4x4man

BG-44K is a fuel system cleaner that actually works.

http://www.bgprod.com/autofuel.html

Bob

bcnet

I have a 2001 Silverado with a start-up knock. But I am also experiencing a ping/knock upon initial acceleration; this occurs on a flat road surface, with no load. If I continue to increase RPMs the ping goes away. It sound very much like a gas related ping you would have with too low of Octane fuel. I have tried mid-grade (89) octane with the same results. I have heard very little mention this problem so I was wondering if I had more of an isolated problem. Thanks

whatsachevy

I have an '01 2500HD with the 6.0. I had a slight ping on pulling inclines. I switched to 89-octane and it did help, but was still noticeable. I mentioned the pinging to my service manager and he recommended reprogramming the computer. After reprogramming (8,000 miles), I switched back to 87-octane and have not heard the slightest pinging since then (now at 12,500 miles). It does seem to help to have a service manager that cares (Henry Marten Chev/Cad/Olds in Leavenworth, KS). I would still recommend anyone with the cold start-up knock to call GM Customer Service at 1-800-222-1020 and request the FREE 5-year/100,000 mile extended warranty. It is true that you have to have your vehicle checked by a GM service center, but my service manager was happy to let GM know that my vehicle did have the cold start-up knock. I don't plan on having new pistons put in (because I don't think it will hurt the engine's longevity), but even if you do have the new pistons installed, you still have the extended warranty (FREE).

bigblackmotor

I have put up a new web site for folks who want to fight GM on the Piston Slap / Cold Start Knock (not the pigning / pre-detonation) problem. GM lied to the dealers and consumers saying they recognized they had a problem and new designs/parts would be available for a retrofit to the engines in early 2002. They now say "Nevermind" its "Normal" and there is no problem.

Join us at http://www.gmpistonslap.cjb.net

It's still under construction so bear with me!

obyone

thanks for the explanation.

joe3891

is on hold because GM has given up development money to sell vehicles,in other words they are broke.

4x4man

Well just got off the phone with one of the people at the dealership. They are telling me the noise is charatoristic of the engine (sound familiar??) and that it is becuase of the fact this engine has solid lifters and it takes a second or two for oil to come up to the top end of the motor when it is cold. I told him that is fine and well, but what is the reason behind it knocking for 2-3 minutes?? He didn't have an answer and told me he would have the service manager call me back. The service manager was supposed to call me in the first place according to the service writter who called me yesterday and told me a similar story that I didn't accept.. So I wait again... I didn't know an overhead cam engine had solid lifters...I thought the cam was over the valves thus eliminating the lifters and push rods...someone want to clarify that for me???

Bob

akjbmw

My direct exposure to Over Head Cam engines is in older BMWs. Cam on top. "Rockers" ride on cam lobes and push directly onto the valve end. These BMWs have an eccentric adjustor on the valve side of the rocker to make the adjustments.
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.. ;-)