Engine Knock

[Rocky]

99 2dr Tahoe LT

 

I am sure glad to hear that others are having ths knocking problem. It fits all of the desrcriptions that are in this forum...loud on start up, ok when warm... Mine had goten really loud when I switched to 10w30. I went back to 5w (both dino) and it got quiet. Also, I had put in a bit to much once 6qts and the knock was gone! Any Ideas?

[WarRaven]

02 5.3 80k.

 

No knock or ticks.

 

Run high grade gas in mine on syn oil.

 

Also, let her run a tach's worth of rpm's atleast once and awhile.

 

And, with every vehicle i have owned, when cold out, run her till atleast the tstat has opened atleast once a day or when used.(Froth free)

 

I never heard of this before the forums here an abroad, and imho, think it may more related to a slight and i mean slight carbon build up with middle to low grade fuel and use of possibly lesser oil filters allowing bleed off, or drain back.

 

 

My old school master, i call him that anyways, got a good chuckle over this, figures its a gateway to mass hypnosis over nothing then some with a legitmate problem and others who have not heard a better then 9.5-1 fire up on a cold morning.(he may be right in my minds eye)

 

Seems odd, fairly tight tolerances on these motors compared to my older sbc's, alot smaller and lighter of a piston aswell, could we just be hearing the bleed off of the oil from journals and lifts, aswell as the shorty pistons seating?

 

in a circle jerk motor, pardon my pun, we slap them together fairly loose, little noisy on cold starts, goes away asa oil pressure is built. runs high rpm's for long lengths of time, with less boring and just honing needed on quick builds.

 

Sorry, i digressed all over the place, just am concerned.

 

Peace out

 

WR

[cbxeric]

My truck has 282000km on it, there's a pretty good knock when it's cold but once it warms up all is fine. It does not use any oil and looks like new.

[yellow z71]

I had an 89 Silverado that did it sometimes. I put 172,000 mi on that thing with the knocking, Finally I sold it just because it had bad tranny mounts and I was too busy rebuilding my camaro to mess with it. I wouldn't worry too much about it.

[dreman]

1999 GMC 4.3 with 244,000 miles. No knock, but a light ticking all the time at idle.

[Angler]

2000 Chev Silverado Reg. Cab 178,000 miles almost put in a new knock sensor and changed my mind, went back to 93 octane no more knocking.

[nxtnlne]

I did have it on my 1999 7.4L 454 Suburban. It knocked loud...till it warmed up.

[billo52]

2003 Sierra 4WD, 5.3L, 71,000 miles, no Knock on 87 octane

[Pugherder]

Mine does it on startup. Worse when its cold. It quits once the oil gets pumping but it takes sometimes about 30 seconds or so.

[no bull]

Yup Got it, 2001 XL 8.1, Around 30 secs at start up ,cold

 

 

Knock Knock

who's there

Mike

Mike who

Mike-chrometer----Hello GM

[BowTieDude]

I originally voted no back in Sept. '06 when I first got my '00. Only a few days later I heard the knock. It definitely is worse when it's cold out, usually lasts 30-45 seconds. If I'm in a hurry and have to drive off without giving it a minute or so for the oil to get distributed it's pretty darn loud. Trucks made it to 164,000+ miles so I'm not too concerned.

 

BTW, this is NOT pinging (low octane) as some have suggested. I know what that sounds like, and this is a metal to metal noise.

 

And as far as GM saying that the noise is "normal" they need to rethink what normal means. If it's "normal" why do some trucks have it and some don't. If there's nothing defective with the engines that have the knock, shouldn't they all make the noise? Does this mean that the trucks that *don't* have it are abnormal? Maybe there's something wrong with them?

 

Normal seems to be GM's favorite word. They could make it a slogan, "We Are GM. We Are Normal."

 

I'll get off my soapbox for now...

[07Sierra07]

2004 with 4.8L the knock has been there since pretty much new.

[jrat88]

2004 with 4.8L the knock has been there since pretty much new.

2001 with 4.8, has the standard knock.

[Westlotorn]

The GM knock is well known in the industry. GM went to very short skirt pistons on the new Generation small blocks. 4.8L, 5.3L and 6.0L engines. These have a lot in common with Race Enignes, Long connecting Rods for good rod angle, Short skirt Pistons for light weight and light tension piston rings for reduced friction. Same things they did in Race engines for last 20 years. It works, very efficient, great power and incredible durability. These are the best engines GM ever made. THE NEGATIVE, GM was new to this Short skirt piston stuff back in 2000 and it took them till 2003 to fix the Piston slap at start up. Once heat hits the piston they grow and quiet down. Colder climates will cause this effect to be larger and warmer climates make it better. Some engines are a little tighter than others and may have no noise, some are looser and make far more noise. They will all run 200,000 miles without breaking a piston skirt which is the only complaint known to be caused by piston slap. If pistons are installed TOO TIGHT they can stick in the bore while you are working the vehicle hard, commonly called Piston Scuff. This problem is far worse than piston slap causing an irritating noise on start up. With this in mind GM was very slow to tighten up the clearance on the new GM family of small blocks. These turned out to be great engines, any production engine rebuilder will tell you they never see one of these in for repair unless the owner abused it to death. No oil changes, overheated it or some combination of these offenses. Hope this helps. Hold the RPM at 2,000 for about 10 seconds to put heat in the pistons and the noise will go away as they grow larger in the heat.

[Westlotorn]

The GM knock is well known in the industry. GM went to very short skirt pistons on the new Generation small blocks. 4.8L, 5.3L and 6.0L engines. These have a lot in common with Race Enignes, Long connecting Rods for good rod angle, Short skirt Pistons for light weight and light tension piston rings for reduced friction. Same things they did in Race engines for last 20 years. It works, very efficient, great power and incredible durability. These are the best engines GM ever made. THE NEGATIVE, GM was new to this Short skirt piston stuff back in 2000 and it took them till 2003 to fix the Piston slap at start up. Once heat hits the piston they grow and quiet down. Colder climates will cause this effect to be larger and warmer climates make it better. Some engines are a little tighter than others and may have no noise, some are looser and make far more noise. They will all run 200,000 miles without breaking a piston skirt which is the only complaint known to be caused by piston slap. If pistons are installed TOO TIGHT they can stick in the bore while you are working the vehicle hard, commonly called Piston Scuff. This problem is far worse than piston slap causing an irritating noise on start up. With this in mind GM was very slow to tighten up the clearance on the new GM family of small blocks. These turned out to be great engines, any production engine rebuilder will tell you they never see one of these in for repair unless the owner abused it to death. No oil changes, overheated it or some combination of these offenses. Hope this helps. Hold the RPM at 2,000 for about 10 seconds to put heat in the pistons and the noise will go away as they grow larger in the heat.