Piston Slap - Anyone have experience with this?

[turbopete]

It appears I have "piston slap" in the engine of my 2002 Chevy Silverado (58K). Does anyone on the board have experience in dealing with GM on this issue?
It sounds like a dead lifter when starting cold, but quiets down as the engine warms up. There are numerous websites and articles on this.
www.pistonslap.com for one.
Thanks.

 

[Whut]

GM TSB #01-06-01-022

"Some of the above vehicles may exhibit an engine knock noise that begins in the first several thousand miles/kilometers of use. The knock noise is most often noticed during initial start-up and typically disappears as the engine warms up. The noise is usually more noticeable when tenperature is below 10 degrees C (50 degrees F) or if the vehicle has not been used for several days. This noise may be caused by an interaction between the piston and the cylinder wall. GM Powertrain engineering, and an analysis of engines returned with this condition, has confirmed that the noise is not detrimental to the performance, reliability or durability of the engine. The noise does not have any effect on the longevity of any of the engine components"


Check out any of the LSx sites like www.ls2.com in the LS1 tech section. You should get some information on what it is but it looks like GM wont do anything about it.

 

[phillyturbosix]

My 98 Silverado does it everytime it starts. My brother bought the truck new and I bought it off him with 70K on it. The sound made him crazy. Switch to Mobil 1 and it will go away or at least make it allot more quiet. I know several people that have well over 300K on that engine with piston slap every morning when they start. There also was a lemon law on this and some people won. But as Whut posted.. GM says it's just typical cold start up noise that does no damage and is fine. Try the Mobil 1 trick. You might be happy.

 

[NJVetteGuy]

My C5 had piston slap. It ran mid 11s all day long on a stock motor with bolt-ons, and 42k trouble free street miles. Car still ran great when I traded it in(back to stock of course), I really wouldn't worry about it. I had over 1000 passes in that car at the track

 

[1987BuickGN]

Mine did it as well. I just ran some top engine cleaner thru it...oh..... 3 years or so and hasnt come back. seems like if you drive the snot out of it (like i do), it keeps it broke up pretty well. LOT of people brought them into the dealerships when I worked there though. They would typically decarbon them once under warranty, then after that, it was your baby. The 6 liters tend to be even worst if you can believe it. No harm being done though as stated.

 

[Dusty Bradford]

My 2000 Tahoe does the same thing. Almost sounds like a rod knocking at start-up and is worse in cold weather. I thought there was a class action law-suit against GM for this issue but haven't heard anything about it lately. Since piston slap doesn't seem to shorten the life of the motor I wouldn't expect much from GM.

 

[phillyturbosix]

There was a lemon law suit toward GM but it was hard to prove as engines with that piston slap have over 350K on them. It's not worth the fight. Try Mobil 1 in your engine and you'll notice it either go away or it will become very quiet. I'm also going to try the top engine cleaner in the spring like 1987BuickGN did. For guys who are into cars, trucks, and engines it's like running your nails down a chalk board for me hearing that in the morning. But after I talked to a plummer who's truck has that famous piston slap sound every morning with 350K original miles on the engine in his 1998 Chev. 1500 I almost don't even listen to it anymore. I just give my self some time in the AM to let it warm up good. I'll report back when I use the top engine cleaner in the spring.

 

[67turboCamaro]

Top engine cleaner will not fix piston slap. The only thing that will fix piston slap is a rebuild. Top engine cleaner is the fix for pre-ignition, also a very common problem in these engines. But it will only fix it for a short period, the carbon builds back up very quickly. Both my 99 Silverado and 99 SS Camaro have both of these problems. I just make sure to give them plenty of warm up time before driving.

 

[Dwayne]

My 95 GM pick-up also had the slap. I went with a thicker oil and it helped quieten it down a bit, the noise went away after about 30 seconds.

 

[The Blob]

And GM wonders why they are losing market share...

 

[turbopete]

Thanks.

Well, it looks like with a good warm-up and changing the oil on schedule all should be fine.

 

[Dusty Bradford]

This issue was addressed in the later model LS motors. I think it had to do with the material the pistons were made of. They required more bore clearance and the slap on cold start was the result. It's been a long time since I spoke with a dealer about it but that's what I remember.

 

[REDS HOT AIR]

put a really big shot of Nitrous on it and the piston slap will go away

 

[TT/Ameasap]

I have a 98 silverado with 153K and it has had piston slap all its life. Just dont beat on the truck and change the oil often....That is my "secret" to a healthy motor life.

BTW, no leaks or oil burning.

 

[Hacksaw]

Sounds like GM should slap around some Engineering Managers for the piston slap. Man, GM says they have improved qualty, and yet they have stunts like this.

For the best fuel & emission effiency they run the coolant as hot as they can. So, you need looser clearances when cold due to thermal expansion, especially aluminum, used in pistons.

Yes, they want to keep rotating mass down, so they shorten piston skirts, hurting piston stability. They want less dead area in the combustion chamber to reduce HC emissions, so they move the rings as high as possible, causing more piston stability problems.

Add all this up, and you get piston slap. GM in the not too distant past used to fuss about ANY noise. Now, piston slap is ok?

Maybe they'll tell everyone to buy a block heater & use it year round!

 

[Loosenut]

My 01 Denali had it. Whenever you started the engine cold it slapped for a few seconds.

I was told by the GMC dealer it is normal and ignore it. The truck had 90k+ on it when I sold it with no motor issues.

-Andy

 

[phillyturbosix]

I just changed my oil on Thursday. Used Mobil 1 the truck sat from noon yesterday and I just started it and it was quiet as a mouse. I'm tellin you guys.. use Mobil 1 and it will either go away or you won't hear it at all. Last oil change I had to use regular oil and all week it was slappin it's a$$ off in the morning. Mobil 1 every 3K and you'll forget all about the slap. 95K on my truck and I drive it hard

 

[67turboCamaro]

I just changed my oil on Thursday. Used Mobil 1 the truck sat from noon yesterday and I just started it and it was quiet as a mouse. I'm tellin you guys.. use Mobil 1 and it will either go away or you won't hear it at all. Last oil change I had to use regular oil and all week it was slappin it's a$$ off in the morning. Mobil 1 every 3K and you'll forget all about the slap. 95K on my truck and I drive it hard

If changing your oil makes your noise go away it isn't piston slap. What you are hearing is yet another problem with these engines. You are hearing the lifters ticking. It is caused by a tore or flat o-ring where the oil pump pick up tube goes in the block. GM estimates about half the trucks sold have this problem due to improper installation at the factory. Watch your oil pressure guage when you start the engine, the noise will go away as the pressure comes up. At start up when the oil is cold and thick the pump will suck air through the tore or flat oring. I had this problem on my 99 Silverado also. It took me about 2 hours to replace the o-ring and now I have one less noise on start up.

 

[BJM]

If changing your oil makes your noise go away it isn't piston slap. What you are hearing is yet another problem with these engines. You are hearing the lifters ticking. It is caused by a tore or flat o-ring where the oil pump pick up tube goes in the block. GM estimates about half the trucks sold have this problem due to improper installation at the factory. Watch your oil pressure guage when you start the engine, the noise will go away as the pressure comes up. At start up when the oil is cold and thick the pump will suck air through the tore or flat oring. I had this problem on my 99 Silverado also. It took me about 2 hours to replace the o-ring and now I have one less noise on start up.

While the O-ring issue does affect some of the LS1s, oil also affects piston slap. My LS1 slaps. Most examples I am aware of do better with non-synthetics. The main reason is that when the engine is cold the natural oils thicken up much more than a synthetic. Rod bearing drag when cold plants the piston on the cylinder wall better. By the time the engine warms up the oil has thinned and the clearances have taken up properly too.

I have tried Castrol, Royal Purple and Amsoil synthetics, the Amsoil being the quiteest. On my car the best oil was cheap Pennzoil 10W30, much quieter than the synthetics. For some reason Pennzoil 10W40 made the whole valvetrain click really loudly. I have not tried Mobil1 though.

 

[phillyturbosix]

I have full oil pressure and it does it till the engine warms up. Trust me it's piston slap. I've done tons and tons of research on this over the past year as the noise makes me nuts. Mobil 1 is one of the only ways to make it quiet down or go away.