Dealer Repair Attempts Failed....?

Doug_Scott · May 22, 2011

Okay! if it is not broken then com back to the dealer after warranty expires and ask the dealer to check the noise, and let' us know what they say...

oh how people like you make my head hurt, i'm going to say this once more VORTECS ARE NOISEY ITS A COMBINATION OF ALUMINIUM SKIRTING ON THE PISTON HEADS THAT NEEDS TO EXPAND WHEN COLD, OR THE VALVES/LIFTERS A PRICE TAG DOES NOT DETERMINE IF ITS PERFECT, YOU SOUND LIKE THE KIND OF GUY THAT NEEDS TO INVEST IN A BENTLEY I HEAR THEY ARE PERFECT BECAUSE THEY ARE A COUPLE 1,000,000 DOLLARS.....

All engines are manufactured with all pieces having certain tolerances. Manufacturers are also trying to get the most efficient engines that they can. They do this by reducing friction as much as possible in the engines roatating mass.

If you happen to get an engine that has just the right combination of tolerances, you will get piston slap, or valve train noise, or engine rotating mass noise (bearing knock, piston pin noise etc). The engine was built correctly, but, it just happened to be at the limits of the tolerances (some parts at max, some parts at min, or even all parts at max). In the case of piston slap, maybe the piston itself is at min, and the bore is at max.

This may not cause harm, but, when one truck does it, and the other does not, the customer should be able to get it resolved somehow, regardless of what they spent to purchase the vehicle. Piston slap was never considered normal operating condition or feature. GM should go over their specs on the engine and move them a thousand of an inch closer to the safe side of the line. As it is now, if you happen to hit the magic combination of tolerances, you get piston slap. They need to make this lottery harder to win.

05GMCZ71 · May 22, 2011

Umm Doug... what's this "when one truck does it, and the other does not" stuff? I think people on here are clearly stating that it DOES happen to others! Sooner or later! There is NO FIX for this. It is acceptable in the automotive industry. You don't have to like it but that's the cold hard truth right there. As others have indicated, it happens on other automakers engines as well. Ford, Dodge, Crapota, Nissan. Cold Start Knock, and slight lifter noise after warm up. You can't fix something that is not broken and is considered normal. the noise is considered normal. Some trucks do it, a few may not. That does not really matter. Sorry, dude.

4wd · January 16, 2012

I put 5w30 synthetic and 10w30 and no change, always ACdelco filters and still have about 20+k before warranty expires, engine is 5.3 aluminum. The valves short knock does not start immediately after engine start..Engine starts normal with normal RPM surge and sound is very smooth for about 15 seconds then after that the RPM drops, you can hear the engine quiets down, at the second RPM drops down to

idle RPM there is the valves knocking for about 10+ seconds...This is the same noise when it was knew and listening to all those who believe it's normal and would not hurt anything I was planning to just ignore it!, but from experience it got worse with time and the noise propagated to the top of the engine and you could hear some kind of steel sharp noises like a whistle. One technician mentioned something about pressure or change of pressure... I believe the root cause is something else and still there, what we did was just replacing the parts that are impacted by the problem. Regarding piston slap, does it starts immediately after engine starts? I mean the from the first second..

I have the exact same noise.Only after a 3hr. or more cold soak. Mine does not start until mine goes to curb idle. After about 15-20 sec. tapping noise starts and lasts for 15sec. To me it sounds like lifter or valve train noise,if i raise the idle when its tapping the noise goes away....I keep thinking lifters Im at 8000k now,it started at 2700 miles, I cant say its gotten worse ,stayed the same I went to the dealer and had them listen to it,truck was there 4hr before they started it , they heard it and told me piston skirts.To me i am not convinced thats the root cause of it At this point Im not sure if it is a piston rattle or liter issue If it is a piston rattle theres not much to do but live with it I'v tried to pull coils one at a time before starting it on 3 separate cold starts.No major difference I thought piston skirt noises,cold start knock were more like a rattle,loud knock??? Can anyone comment on that?? Thanks Chris

Chris, have you managed to get it fixed?

Any comment/update?. Thanks

Gurrzt · January 16, 2012

As I mentioned in an earlier thread, I have a short cold start noise which lasts for about 20-30 seconds (very annoying!) dealer first replaced all lifters but noise was worse after the repair, then called me two months later and replaced all lifters again, oil pump and cam. During the first week after the second repair the noise almost disappeared, now it's back but not as bad as it used to, when the service manager heard it he said this is valves tapping noise.

After the second repair the guy who worked on it was sure the noise will not come back, he said he cleaned all carbon deposits and cleaned the valves that was sticking, but he advised me to use higher octane which I did.

When engine is worm, no noise whatsoever. It's only when I start it in the morning or after it was sitting 3+ hours, out side temperature is not a factor.

To me it seems an oiling problem, but the tech comment about carbon deposits , valves sticking and using higher octane is confusing, oil pump was replaced twice, but after the last repair the pressure gauge started to move with RPM which I think is good thing, dealer put the right oil and filter and oil consumption is very very little so far.

Still under warranty and don't want to push for new engine, because I may end up with the same issue.

What do you think?

I am also a owner of a 2001 Z28 Camaro with a Gen III aluminum block (steel sleeved) 5.7L (348 cid) engine. It is very common for these engines to have what is called "piston slap" on startup. It is a "ticking" that usually lasts 30 to 60 seconds until the engine starts to get warm, when warm the sound goes away totally. The cause of this (has been hottley (sp) debated) is the dis similar metals of the block to the piston sleeve, which when starting up the engine, it causes the piston to slightly rattle, which causes the tick. Once the engine is warm the sound goes away because both dis similar metals have expanded back to their correct tolerences

.

My 2001 Z28 (Sara) uses 1 qt of oil every 3K miles, however I drive this vehicle very aggressivley . I have owned Sara since new (12/00), and find this condition has no effect on performance or reliability. I CAN TEAR UP THE ROAD WITH THE BEST OF THEM

Please understand that I am BY NO MEANS a expert on anything automotive please refer to the below article for a more intelligent answer:

http://www.pistonslap.com/tsb.htm

4wd · January 17, 2012

Thank you for the comment, but how come some alminum engines, I mean the same engine and gmt900 don't have the piston slap? mybe the good ones have the right tolerance!, anyway, since it's piston slap then GM/dealer can go in and repair it by puting the right size cylinder/cylinder head.

Thanks again.

Gurrzt · January 17, 2012

Thank you for the comment, but how come some alminum engines, I mean the same engine and gmt900 don't have the piston slap? mybe the good ones have the right tolerance!, anyway, since it's piston slap then GM/dealer can go in and repair it by puting the right size cylinder/cylinder head. Thanks again.

Unless your engine is consuming alot of oil, I would let it be. Rather than re sleeving your engine, it would be easier to install a new create motor, but why? I know people with blown to turbo and Nitros LS1's with piston slap, that put out over 600 RWHP and up to 700RWTQ that other than the tick noise run in the 7 range 1/8 mile, and tear up the quarter mile in the low 11's.

My engine has had piston slap from day 1, and runs like a raped ape down the road.