engine detonating (knocking)

[frankendart]

Are you fellas talking about PISTON SLAP? If so, save your money. It's not a problem with bad gas, or anything like that. It a piston problem.
The piston has a short skirt, and, is actually a little small for the cylinder bore. When you start your truck, it sounds like a diesel. Usually, once it warms up the slap will go away because the piston expands as it gets hot.
GM claims that it "NORMAL" and "HARMLESS" to the engine. I just can't imagine how a piston wobbling and knocking against the cylinder wall a couple of thousand times a minute could be normal, much less harmless.

I've read that the cylinder walls are pretty well scored by this when they tear down the engine. I've also read that trucks with this problem suffer from poor resale value, too! That makes sense. I know I would buy a truck that sounded like that. Would you?

I understand that the '03 trucks are supposed to have been cured of the problem. Tefloned pistons are supposed to stop the noise.

You have to wonder why GM would spend the money to try to fix something that is suposed to be "Normal and Harmless", though....

Just my humble opinion.
Frank

[dk 55belair]

Originally Posted by silverado01

my 01 Z71 knocks so bad it sounds like a rod is going through the oil
pan. I have heard the same as all of you, normal noise etc.

my 2001 silverado with 35,000 miles knocking and im recieving the same runaround from the service dept and gm. does anyone know if a class action lawsuit has been taken against chevrolet. i want in. for 26 yrs ive drove chevys and own 6 right now, im so mad i cant stand it.

[frankendart]

Originally Posted by dk 55belair

does anyone know if a class action lawsuit has been taken against chevrolet. i want in. for 26 yrs ive drove chevys and own 6 right now, im so mad i cant stand it.

I haven't heard anything about a class action law suit. There was a web site that covered piston slap, and had link to lawyers. I suppose that was the beginnings of a class action, but the site was shut down by the courts. I think GM had something to do with that(?).

Many Chevy guys are finding that thier new (99-03) trucks have more comfort and drivability, but the VORTEC engine is not as good as the good old 350 was. I own a 2000 Silverado, and while it's appointed much better than any p/u I've had in the past, I wish it had a 350.

I find myself trying to figure out why GM would design an engine with the potential for something like piston slap. It seems to me that someone in R&D would have known the the VORTEC had a problem, long before the engine was put into production.

My opinion is that R&D knew there was a problem, but the bean counter, the guys with the check book, who really run GM, made the decision to go ahead with it anyway, because of the dollars already spent. The gamble was that only a fraction of the engines would develope a problem, and of those, only a smaller fraction of people would open a law suit about it. Still a small number would win their law suit.
It was a calculated risk, and so far, it would seem that they were right. GM has produced defective engines, and no one has held their feet to the fire for it.

While my Silverado does not have a slap problem, and it now has 80,000 miles on it, I do know two people who's trucks suffer from piston slap. Neither of them have recieved any help from GM, and they can't sell the trucks for anything near what they should be worth. It's truly a shame, and I feel truly sorry for them. They are both diehard "CHEVY-GUYS", and GM is doing nothing to pay back the decades of loyalty both these men have shown.

I'll be looking for a new truck when the '04's come out. Because of GM's lack of response to the problem, I'm not sure that I want to RISK another $25,000 to $30,000 dollars on another Chevy. For the first time in my life, I'm actually considering buying a Toyota !!! I've heard and read all the pros and cons about the Tundra, and the pros far out weigh the cons. I know a few people who own Tundra, and all of them rave about the trucks. Most of them are former Chevy buyers. There must be something to it!

Last night, during a conversation about what my next truck will probably be, my buddy (a life long Chevy buyer, and a former '01 Silverado owner) told me that he had, "...forgotten how good it feels to own a truck as dependable and trouble free as his Tundra". I've found that that's the typical response from Toyota owners. I remember when it used to be what Chevy owners said.

That's my

[mjrodney]

From the GM Technical Bulletin on the subject....

Info - Engine Knock on Cold Start #01-06-01-028
Engine Knock on Cold Start
1999-2002 Chevrolet and GMC C/K Pickup and Utility Models

2002 Cadillac Escalade (2WD)

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, U -- RPOs LR4, LM7, LQ4)

Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000 km (12,000-15,000 mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30 seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.

This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.


Important
At this time, attempts to repair this condition by replacing the engine assembly or pistons is not recommended.


Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions, please have the customer contact the Area Service Manager.

[djpbaby]

Here is the latest bulletin on the topic. My brother, best friend, my two uncles and I all own newer Silverados. My one uncle has a newer 2002 that does not have the problem. Everyone else does. One GM mechanic told me that it is the lightweight, short skirt design of the piston. It is short enought to twist slightly and slap, especially when carbon build up and the engine is a little cooler. It is a really bad design because if there is a real problem like a bend rod, crooked lifter bent valve or the like, you would just be told that it was a normal sound and you'll just have to live with it. I've got 80,000 on my truck and it still runs fine. I would be interested in hearing from someone that there engine blewup because of that problem.

Engine Knock on Cold Start
1999-2002 Chevrolet and GMC C/K Pickup and Utility Models

2002 Cadillac Escalade (2WD)

with 4.8L, 5.3L or 6.0L Engine (VINs V, T, U -- RPOs LR4, LM7, LQ4)

Some of the above vehicles may exhibit an engine knock noise that begins in the first 19,000-24,000 km (12,000-15,000 mi) of use. The knock noise is most often noticed during initial start-up and typically disappears within the first 5-30 seconds (may last longer in extreme cold temperatures). The noise is usually more noticeable on the initial start-up when the temperature is below 10°C (50°F) and may be more pronounced on the first cold start following a long trip.

This noise may be caused by an interaction between carbon that has formed on the piston, the piston motion and the cylinder wall. GM Powertrain Engineering, and an analysis of engines with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. THIS NOISE DOES NOT HAVE ANY EFFECT ON THE LONGEVITY OF ANY OF THE ENGINE COMPONENTS.


Important
At this time, attempts to repair this condition by replacing the engine assembly or pistons is not recommended.


Please share the information found in this bulletin with customers who inquire about this condition. In the event they have additional questions or concerns, please advise your Area Service Manager.

[fastchevylover]

guys they knock because they either aren't getting tje octane they need or because your timing is advanced to far. so if a fuel additive doesn't fix the problem go to an auto parts store and rent a snap-on timing light and down you dwell and timing. also it might be your points (if your using an old distributor) but those take some time to get back in the right spots. and if you dont know what your doing its a real bitch! so i would advise against playin with those.....hope this helps boys!

[frankendart]

Originally Posted by fastchevylover

guys they knock because they either aren't getting tje octane they need or because your timing is advanced to far. so if a fuel additive doesn't fix the problem go to an auto parts store and rent a snap-on timing light and down you dwell and timing. also it might be your points (if your using an old distributor) but those take some time to get back in the right spots. and if you dont know what your doing its a real bitch! so i would advise against playin with those.....hope this helps boys!

Points? Distributer? These trucks have neither.

My buddies truck is serviced by the local Chevy dealer. If they can't get it right, who can??? His truck suffers from piston slap, not low octane knock. He runs 97 octane gas, and has since he bought the truck.
*He's had it "DECARBONIZED", to no avail.
*He was instructed by the dealerdhip to change the brand of oil and filter he uses. But, since the Chevy dealer does his oil changes, he left it to them to use the "right stuff".
*The dealership mentioned the higher octane thing, but he already uses premium gas.

He told me that one of the techs at the dealership mentioned replacing the pistons with teflon coated pistons. That has not been done yet, but all of the other so called "cures" have. He's extremely unhappy with his truck, and I can.'t say that I blame him. It sounds like a diesel!

It's not a distributer problem, or points, or octane, or timing, or anything like that.

It was explained to us by a GM tech that, the piston, when cold, is actually too small for the cylinder bore. That, coupled with the very short piston skirt create a "piston slap" situation during cold starts. The piston actually wobbles in the cylinder bore, and the bottom of the piston, the skirt, "slaps" the cylinder wall, thereby make the knocking sound. As the engine temperature rises, the piston swells enough to fill the bore and reduce or eliminate the slap. Now, I'm not a GM technician, nor do I claim to be a master mechanic. But, that explaination makes sense. As does the theory that along with slap comes scoring of the cylinder wall. doesanyone think that a piston can wobble in a cylinder a few thousnad times a minute, and not cause some kind of damage to the cylinder wall, or piston, itself?

I've read that some people have gotten free extended warranties, replacement pistons, or even replacement engines because of this. As far as I can tell, Gm's reaction to this problem is spotty, at best. Their standard line about the sound is "It's normal". What is so normal about an engine knocking? If we were talking about a 350 making this kind of noise at 15,000 miles, the dealer would replace it in a "Heartbeat".


I don't have any first hand experience with this problem. Nor do I claim to have any more knowledge than any of you. As I stated in another post, my truck, a 4.8 Silverado, has 80K miles on it, and it does NOT have a slap problem. It also doesn't consume oil between changes (which is also "normal" according to GM) like MOST vortec engines do. But, I'm watching a very close friend of 20 years deal with it. He's getting the run-around from the dealership and GM, and it upsets me to no end. They didn't hesitate to take his $28,000.00 when he bought the truck, but they sure do balk when he brings it back to get repaired!
It's because of his experiences, and those of a fellow employee at work, that I'm considering a Toyota
If I wanted the fastest I'd buy a Lightning. Or, if I wanted the most powerful, I'd buy a diesel. I'm looking for dependibility and reliability. Unfortunately, In my opinion, GM is not offering that at the moment. For that matter, neither is Ford or Dodge.

Do any of you really believe that GM designed these engines to make this sound, and consume oil at an accelerated rate, on purpose?REALLY?

[Procharged LM7]

I guess noone here has ever experienced F Bods or Corvettes either????
Almost all the Gen III's have this noise. My truck started doing it at 10,000 miles. I have ran a blower on it for the last 3,000 miles, and it hasn't broke it, and I know of several other Gen III trucks that are over 100,000 miles, and make the same noise, and have since they were fairly new.
My ex GF's Subaru had a REALLY loud knock at startup, and less when it warmed up but still there, and the dealer service dept gave us a Copied paper explaining piston slap, short skirt pistons, etc. So it's not just GM that has the same deal.
It's not carbon, it's not injectors, it's not detonation. It's the short skirt pistons, and bore clearances required to operate the way they do.
Millions of F bods can't be wrong.

[frankendart]

Originally Posted by frankendart

Do any of you really believe that GM designed these engines to make this sound, and consume oil at an accelerated rate, on purpose? REALLY?

[gmt560]

Sounds like we all have something in common. My 03 Silverado w/5.3L started "pinging" under light acceleration and pings a lot at highway speeds when you tip the throttle such as going up a slight grade. This started at 5,000 miles (currently 7k on OD). Likewise a heavy, horrible rotton egg smell started coming from the tailpipe. Has anyone else got this odor with their engine problems?

Dealership passed it off as bad gas but I dont put off-brand gas in 34 grand worth of truck. Tech 2 analysis revealed the ECM is controlling timing like it should. Fuel pressure regulator checks out ok. They replaced the O2 sensor in bank 1 and it still pings. Dealership says "trace" ping is normal but I dont consider this "trace" ping. My wife who is normally oblivious to anything mechanical even noticed the ping! That's bad.

Dealership also says exhaust odor is normal and proof the catalytic convertor is working. Sarcastically I told them GM must be worried then because every other Silverado I have ridden in (most friends have them) do not smell so their convertors must be defective. Dealership did not appreciate that.

I'm at a loss. Someone suggested the converter may be plugged but I figure something else had to be wrong to plug it right? Any help will be appreciated. Dealership running out of patience and so am I. Thanks.

[Tonny Berkman]

Hay budd ,Im havig the same problum with my 2001 Silverado.
You cant here it when I first crank the truck BUT,after it sits idling for about 20 minutes it sounds like the valves and a rodd is coming apart.
The trucks only got 27000mls.,on it.the service manager at a chevy deiler told me that was normal for those 4.8 V8's with aluminom heads.
Let me tell you a little secret it isnt normal.

If you find a fix please e.mail me at
[email protected]

[Tonny Berkman]

Well I don't know what to say or do.Ive heard things from bad plugs and coils,to short winged pistons.Im not douting none of this,becouse Ive not put the first rench on my truck except to change the oil.

All I know is that Ive been to two chevy dielers and Ive got the same runn-around.The same thing was said ,Its a normal thing for these
motors to sound like this becouse they have aluminom heads.


He told me that the all aluminom motor that there working on is going to be worse.

Me being an active dragracer,and building a couple of thumpers myself,and after 16 years of throwing renches,I know when someone is pulling the wool over my eyes.

People have asked me why dont I let it go,and fix the truck myself.;;Why should I,thats why we pay all that extra for these newer trucks with a warranty.

They even told me in (so many words ),that they wouldnt honer the warranty becouse I didnt buy it from a chevy dielership. I was reading an artickle a little while back where Chevy was manufacturing there motores in Mexico,NOT here in the United States.

All I know is Chevy has got a parts defection on these motores and becouse it has not become a health concern ,or a fire concern they wont do anything about there defective parts.

I honestly believe that for what I payed for my truck it shouldnt make a peep.

[frankendart]

Tonny, I hear you, man, and I agree with you.

For months I've been asking a few questions of member of this board, and other boards, who consistantly defend GM when it comes to the quality of their engines.

I have no problem with the quality of the Chevy and GMC pick up trucks, themselves. I believe the quality of the vehicle is as good as anything else available, and better than most. It's the engines that seem to be the biggest problem. That and the standard line people get from the dealerships, "It's normal", or "There's nothing wrong that we can find", or "we checked it out, and it is within normal guidlines".
It's enough to make you want to scream!!!

When a working man (or woman) finally gets to the point where he can afford to drop $22,000 to $35,000 for a new pick up truck, he has every reason to expect that truck to be flawless, and free of defects. As far as I'm concerned, that is an assumption that I can no longer make when buying a new GM built truck. There will always be that haunting doubt in the back of my mind that the engine could develope a knock, or a ping, or whatever, and the dealership will not stand behind me. What's worse, It seems GM won't help, either!

One of the questions I asked was this:
When you go to buy a new truck, and you pay $26,000.00 for it, how many defects are acceptable to you?

My answer is, of course, NONE! But that is not the answer that many Chevy loyalists gave!?!?!?!

Some have defended GM by answering: "... well they make these trucks so fast that some defects are bound to happen" What?!?!?!?

Another answer was, "...My truck doesn't make any sounds, maybe you should check you oil oncein a while..." Again, WHAT?!?!?!

The consensis seems to be that is only a few trucks are having this problem, and it's not my truck, well than maybe it's not really a problem.

Wheather you have a problem vehicle or not, the question is still the same:
Should GM take responsibility for defective engines, if the defect becomes evident while still under warranty?

My answer to this would be, YES!

I would add to that: Should they accept responsibility for engines that show these defects after the warranty expires, IF that engine type has a history of THAT PARTICULAR DEFECT?

My answer to this would be, Yes, because if the problem was known to exist, GM should have voluntarily recalled the defective engines and repaired or replaced them. In my opinion, leaving the buyer with a defective vehicle is just poor business practice.

I will be in the market for a new truck after the holidays. I will, of course, go to the Chevy and GMC dealers first, because I like GM's trucks. But, for the first time in a long time I'm going to be taking a serious look at the other guys, too. Not that I think their trucks are any better than Chevy's, (personally, I think as long as you buy a full size truck, it's difficult to get a bad one. I have no use for mini trucks, just too small for my 6'3" 235 lb frame) but because I believe the support from the dealership, and the manufacturer might be better. It certainly couldn't be any worse, in my opinion.

[Tonny Berkman]

Originally Posted by frankendart

Tonny, I hear you, man, and I agree with you.

For months I've been asking a few questions of member of this board, and other boards, who consistantly defend GM when it comes to the quality of their engines.

I have no problem with the quality of the Chevy and GMC pick up trucks, themselves. I believe the quality of the vehicle is as good as anything else available, and better than most. It's the engines that seem to be the biggest problem. That and the standard line people get from the dealerships, "It's normal", or "There's nothing wrong that we can find", or "we checked it out, and it is within normal guidlines".
It's enough to make you want to scream!!!

When a working man (or woman) finally gets to the point where he can afford to drop $22,000 to $35,000 for a new pick up truck, he has every reason to expect that truck to be flawless, and free of defects. As far as I'm concerned, that is an assumption that I can no longer make when buying a new GM built truck. There will always be that haunting doubt in the back of my mind that the engine could develope a knock, or a ping, or whatever, and the dealership will not stand behind me. What's worse, It seems GM won't help, either!

One of the questions I asked was this:
When you go to buy a new truck, and you pay $26,000.00 for it, how many defects are acceptable to you?

My answer is, of course, NONE! But that is not the answer that many Chevy loyalists gave!?!?!?!

Some have defended GM by answering: "... well they make these trucks so fast that some defects are bound to happen" What?!?!?!?

Another answer was, "...My truck doesn't make any sounds, maybe you should check you oil oncein a while..." Again, WHAT?!?!?!

The consensis seems to be that is only a few trucks are having this problem, and it's not my truck, well than maybe it's not really a problem.

Wheather you have a problem vehicle or not, the question is still the same:
Should GM take responsibility for defective engines, if the defect becomes evident while still under warranty?

My answer to this would be, YES!

I would add to that: Should they accept responsibility for engines that show these defects after the warranty expires, IF that engine type has a history of THAT PARTICULAR DEFECT?

My answer to this would be, Yes, because if the problem was known to exist, GM should have voluntarily recalled the defective engines and repaired or replaced them. In my opinion, leaving the buyer with a defective vehicle is just poor business practice.

I will be in the market for a new truck after the holidays. I will, of course, go to the Chevy and GMC dealers first, because I like GM's trucks. But, for the first time in a long time I'm going to be taking a serious look at the other guys, too. Not that I think their trucks are any better than Chevy's, (personally, I think as long as you buy a full size truck, it's difficult to get a bad one. I have no use for mini trucks, just too small for my 6'3" 235 lb frame) but because I believe the support from the dealership, and the manufacturer might be better. It certainly couldn't be any worse, in my opinion.

frankendart;;,and anyoneelse;;,
This is just my vew;For those who are dyhard Chevy fans theres one thing that we have to look at,

1,You eather did not get stuck with a truck that has this problum. OR.
2,You have a close inside,relationship with a Chevy Deilership. OR.
3,You have been one of those guys who buy there Chevy and deck it out with all the goodies,and its probably to late do anything about it now anyway.
OR.
4, Youre just like the rest of us ,you love youre Chevy,and you would rather have youre truck fixed wile its under warranty than trade the brand of truck.


You know every time I come out of a store I look over at my truck and I have to admitt that its the best d?mb looking truck in the parkinglot.,..BUT.,when I stop and think of what is rong with my engine all the nice feelings I had about my truck just whent down the toilet.



Lookes are not everything.,you have to look at dependability as well.Im expecting my wife to call me at work one day and tell me that the motor has let go and her and the kids are strandid somewhere.I guess we can all thank Chevy manufacturing for that.

[CY-TEX]

I have gone many rounds with the dealership and GM over the knocking sound coming from my truck. I have a '00 4.8 L silverado. I was told by the dealership that it was a "Nuisance" noise that GM was aware of, but that there was no adverse affects to the longevity of the engine. HOGWASH. It doesn't take a rocket sceintist to tell you that if there is a knocking noise coming from your engine, it is because of something interferring with something else. That can't be good. Anyways I was interested to read the reply from the gentlemen earlier that said he heard it was affecting resale values. I went in last week to trade into another vehicle and they offered me $8000 for it. This is a '00 4.8L w/ 40K miles all power, not a scratch, burn, dent, ding, stepside bed, etc.. and I thought that was extremely low.. KBB qoutes trade-in @ 11,700 and private seller @ $13,800... interesting... did the dealership hear that knocking, and low-balled me on purpose because they don't want my truck??? if it is O.K. for us to have to deal with it, then it shoudln't affect trade-in right??