knocking engine info

[THE BIGPUNN]

i spoke with gm service manager at my local gm shop. he explained to me that the knocking noise problem has been a concern of several truck owners. he said GM claims its normal engine noise. he said the problem they found at his shop is carbon buildup on pistons. he said that they have a cleaner solvent that they can pour in the engine, they let the truck sit over night and start it in the morning. he said it seems to solve the problem for some time, but has to be repeated every so many miles. i plan on having this done to my truck for the heck of it on my next service.

[RyanbabZ71]

he said GM claims its normal engine noise. he said the problem they found at his shop is carbon buildup on pistons

 

2 emails to chevy and i was offered a 5 yr/100K mile engine component warranty.  I dont think the problem is normal

 

I actually had a long conversation in class and with my thermo teacher.  Bascially the summary engine knock isnt good and there can be many reasons for it.  Teacher didnt exactly know what my situation was said it sounded like a rich fuel mixture at startup

[NewbieZ71]

Ryan, did you have to have a dealer look at it or anything?  You got a 100K warrantee on engine parts for just writing an email?

[RyanbabZ71]

i had it checked out at 7073 miles i believe it was.  7000K some odd miles.  Foreman said it was normal so i left it at that and never thought about it.  Back in this past late summer early fall i talked with my service advisor about engine knock and she said gm issued a tsb saying its normal i said so i shouldnt bring it in then? She said no its a waste of time bring it in if they ever issue a fix.  

 

So yes i did have it checked at the time they didnt characterize it engine knock but an engine noise.

[Greg]

I had the same problem with my 99 Sierra and it's starting with my Av (now at 11K miles).  Eventually on the Sierra it led to a sticking throttle when trying to push down on the pedal.  I had 2 non-warranty-covered cleanouts done on the Sierra at about 30K intervals and the noise and sticky throttle disappeared.  My GMC service manager said it was a common problem and he heard it was caused by recent changes in gas formulation.

[radrado]

he said the problem they found at his shop is carbon buildup on pistons. he said that they have a cleaner solvent that they can pour in the engine, they let the truck sit over night and start it in the morning.

Do you have any idea what this product they pour in is?

[NewbieZ71]

I guess my question is did GM check on your service records to verify you had complained of the knocking?

[RyanbabZ71]

i am sure they would have.  I mean i gave them my vin cant be to hard

[THE BIGPUNN]

i'll see if i can find out what the cleaner is and keep you guys posted.

[RyanbabZ71]

gm top end cleaner is the name of it

[RyanbabZ71]

gm top end cleaner is the name of it

[THE BIGPUNN]

ryan, have you already had this cleaner done? do you know whats in the stuff? any results?

[RyanbabZ71]

never used it

[sierra1]

I don't really believe the story about carbon buildup.  ####, my exhaust pipe is still silver inside at 20K+.  I think the startup noise is piston slap, at least I hope it is, and the pinging when driving is the timing and/or slightly too hot spark plugs.  I pulled one from each side and they looked way too clean for 20K miles.  My friend has the little scope thing that you can see inside the cylinder with, (I used to have one, but I dropped it once and it never worked again, I can't remember the name of it) I looked in both of the cylinders I had plugs out of, and they looked really clean, only a small amount of anything dark right under the plug, and it wasn't much.  The intake valve was down in one, and it looked new, not a speck on the back of the head.  My 77 Dodge 360 had a bunch of crud on it by then! Of course, it took leaded gas..

 

What I do to keep the knock down:

 

Use 88 octane gas or better, I usually fill the tank at the halfway point and put 87 in one time, and 89 the next, it seems to be enough to keep it down.

 

And the most important thing I do is drive it hard as much as possible, it idles much smoother afterwards, and almost never pings if I get on the freeway twice a day at full throttle up to about 70, and then back off to 65.  

 

When it goes in for the 24K service, I will make my second complaint about start up knock.  The other isn't a big deal as far as I can see.

[Roger]

Concerning the carbon build up-

 

When I had the knocking with my 98 Ram, Dodge several times used a cleaner solvant like what is mentioned here. The knocking still came back.

 

While I had the knocking, there was 2 times that Dodge told me to use the 91/92 octane fuel to lessen the knocking (I wasn't using cheap gas either-99 pecent of the time I used Chevron, which by the way was also the recommended fuel to use by Dodge). Finally they had to do a valve job because of the problem. The advisor called me up and said he found what was causing the knocking-it was due to excessive carbon build-up, which, when I asked him what caused it, he said using too high octane fuel. I then reminded him what Dodge told me earlier and what I had been using.

 

With no additional comment concerning the high octane use, he said that from now on I need to use 87 octane fuel only.

 

Less that 3 months later the knocking was back (and even worst now). Took truck to Dealer and they once again comfired with Dodge in Michigan. I was then told "the knocking and pinging is normal, it doesn't damage the engine, and BTW you need to use the highest octane fuel possible to lessen the knock."

 

That was when I got hold of a lemon law lawyer and that is why I now own a 01 Silverado and not that RAM.