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Engine Knock on 2001



Hello there,

Has anyone had a problem with an engine knock? My 2001 has this knocking sound in the engine. Kinda sounds like a dull lifter knock, but coming from the bottom of the engine. Particularly loud when it is cold outside and just fired up, and faint when warm. The car has been babied from the time purchased brand new. I've scheduled an appointment with the dealership for this week, just wondering if anyone has heard of this. Thanks,

I'm not sure, but someone will respond to your post who can help you. Just be patient. Good luck with the dealer. Do you use premium unleaded (92). Some times the engine pings and knocks if 91 or higher is not used.
Engine Knock

Thanks for the encouragement. I always use 92 or 93 octane when filling up. I just read a thread about 3 months ago dealing with the gentleman with the blown engine and the legal problems with GM. I'm sure mine is not to that point (I hope not), although the knock has gotten proggresively worse the past few thousand miles. I'll let you know the outcome...

Have you brought the car to a dealership to have them look at it?
Questions please

Hi there, and welcome,
As for your issues, what is the mileage????
How long have you been experiencing this condition???
How long after initial cold start does the noise last, in minutes??
Please let us know what you have, c4c5
Hello again,

It's a C5 with 8000 miles now. There was always a faint "slap" in the engine, but the knock started about 1000 miles ago and has gotten louder since. It will last for about 8-9 minutes, then into a faint knock when it idles at about 1100 RPM. Is this a normal function?
I have had this knock from new on my 2001. It starts about 40 seconds after cold start up. It is really noticable for about 5 mins there after. Then its still there hot but really faint. I was told there was nothing wrong with the engine and is a trait on cars with no piston skirts. GM changed the design in 2000. They were to have coated the pistons with something for 2002 to reduce this noise. I must admit every time I hear it on start up Im troubled by it.
Most likely, CARBON

While you issue is not uncommon, your clue here is the getting louder as time has gone on. Here are the details
As the design of the pistons have very little in the way of piston skirt, they do rock slightly in the bore. Now, this is the design, and will not create any problems, but as you mileage grows, so does the deposits within the combustion chamber. So what this does it change the way the piston moves, causing the increased noise.
I would say that they will most likely do a top engine cleaning, and have it soak over night, to see how it does.
Please let us know how you do, c4c5
I also had this same problem with a 2000 S10 Blazer. They did many Top engine cleanings. Nothing helped. They ended up replacing the engine and that did the trick. Then different problems came up due to the engine not being installed properly and I ended up suing GM they setteled out of court for 60K
I would sure hope it doesn't come to that. I can't comprehend the thought of a new engine being put in my baby. :( My appointment was moved to next week because of me, but we will see what happens.
Oh I would never go through that again. I should have just traded the thing in, it took 14 months to get resolved. I had another 2001 a coupe that had the knock as well but not quite as pronounced. I had Dave Peice (Chevrolet Brand Service Mgr. from Warren Mich.) look at mine and he called it "piston stack up". He explaned that sometimes a block may have a bore that is just a tiny bit to large and the piston put in that bore might be a little off as well (too small) and this is known as "stackup". This causes piston slap and assured me that it will cause no harm. He told me that the 2002s had this problem addressed with some type of coating to the sleeves and pistons. This leads me to think the problem or as GM would like to address it as an "annoyance" is fairly wide spread. We just got cars that are a little louder. (Of course I would get the noiser one)
The carbon build up, and stack up, are the same condition

Black Ice,
As for the information that Mr Peacy, has provided to you, this is true, however, this is a different concern, as you saw from the post, this condition has worsened over time, due to carbon build up. Normally, stack up does present itself, but does not get progressively worse, it stays at one noise level, and does not increase. However, the principal is the same, piston movement.
As for your Blazer, these are 2 different engines, and should not be confused.
The same condition presents itself, as movement of the pistons in the bore, is aggravated by the carbon, thereby, increasing the noise.
Please do not consider this aggressive, this is just the way this design is, and the pistons, and rings were updated for the 02 model year.
Just a Mr Peacy has said.
Best to all, c4c5
Peacie also said it could be a wrist pin problem.
I had to move my appointment and it's going in Tuesday, we'll see then. I'm not too optimistic given what everyone has said, but you never know!!
Ok, here is the latest on the knock... They say that I have a bad lifter and possibly a vavle problem. They have ordered new lifters and have scheduled to put them in next Wednesday. They need about two days to do it. Whew.....Just the thought of my heads coming off makes me sick to my stomach. :puke He assures me that the best will be working on it (like he'll tell me his worst guy will be on it) and it'll be fine. I guess we shall see. Thanks everyone for the advice and info here.
Oh please keep us informed. I have this same noise. I would like to see how this works out for you. I may be next!!!
c4c5specialist is right.

Some pre-02 Gen III passenger car engines have a problem with "cold piston knock". It has to do with the shape of the piston, the piston-to-bore clearance and how that clearance changes as the engine warms.

It is not a problem, just an annoyance.

All the symptoms listed here speak of a noise that is louder at start-up than it is after the engine warms. That is typical of cold piston knock and NOT typical of detonation or "spark knock".

The piston design used in the LS1/6 engines was changed for MY02 to eliminate this problem. Details of that can be found in an article on the 02 LS6 in the new GM High-Tech Performance that should be out about now. Information on the new piston can also be found at:http://www.c5registry.com/2k2z06/
Very interesting Hib, My 2001 was made in mid May and GM claims the pistons were changed in Mid April and I still have the knock as well.

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