My '02 with 18k miles has and has always had a tapping noise until engine is completely warmed up. I recall seeing something last year on the Forum about this problem. It seems like there was a service bulletin out about this problem and that it had something to do with an O-ring in the oil pump or something similar.

Before I get flamed about not using Search, I tried but all I get when I try to go to Search is the ole "This page cannot be displayed" sign.

Can anyone give me info about this problem and where to locate the service bulletin?

 

well where is your oil pressure at start-up? if it was a pinched o ring there would be psi problems all around. piston slap? what kind of oil and filter you run?

 

Welcome to the world of the dreaded "Piston-Slap."

From what I understand, the cylinders were designed with just a little bit of extra space and so it takes a few moments for the pistons to warm up and expand enough to eliminate that extra space and for the noise to go away.

It bugged me at first and I did all the usual complaining to GM and all I got was a 100,000 mile engine/powertrain warantee in case it ever does kill the engine, so to speak.

Just gradually warm up your car by drivinig slow and easy for the first few minutes or so and you shouldn't have any problems. For more info, do a Google search for "Piston-Slap."

 

Over the years GM has used a few different alloys in the pistons. Some of them have rates of expansion such that to fit well after warming up, they are a little small when cold and have a bit of slap noise until they warm up. There are plenty of people on this and other forums that are big proponents of the very thin oil specified by GM for this engine. Industry insiders have told me that the use of thin oil has more to do with improving engine milage ratings in the short term to establish higher vehicle MPG ratings and Corporate Average Fuel Economy ratings,, but has nothing to do with long term longevity of engines. Over the past 40 years I have know a number of custom and race engine builders. ALL of them have been very strong about NOT using thin weight olils in an engine you expect to last a long time, or be subjected to higher loads. Given the experience and advice of REAL professionals, not some hobbiest that parrots the factory story, I have chosen to run Mobil One 20-50. My 98 had about 64K miles on it when we bought it. It had a bit of the piston slap, clearly audible when cold and that would last until engine temp came up to about 165 or so. At the first scheduled oil change, we installed Mobil One 20-50 and found an immediate reduction in cold piston slap, and a cessation of it in less than a minute from startup, FAR less than before. Oil consumption has fallen to as close to zero, compared to 1/2 quart in the ' onboard computer calculated oil change period'.. Please also understand that piston slap is NOT caused by lower oil pressure. ANy noise that is related to lower oil pressure will be bearing knock of some kind. The cylinder bore/piston interface is oiled by splash from the crankcase. With the thin oils specified by GM, there is little film that remains in place when the engine is shut off, as it is thin and runny. When you start up the engine, there just isn't much film to protect and cushion the pistons. With a thicker oil the remaining film in the cylinder interface is thicker and provides a little more cushion, hence is quieter, AND leads to longer service life.

I would NEVER run any of the 0-5, 0-10, 5-10, 10-20, or 0-20 oils that are so popular these days, regardless of brand, in ANY vehicle I own. They may be good for short term reduced spinning friction, and hence good for higher milage ratings, but my expert engine builders tell me they are terrible for engine protection and long life.

I DO suggest following the advice to use a high quality synthetic oil, as they as a 'family' of oils seem to have far better resistance to heat breakdown, maintain lubricity longer, and deal with contaminates better than regular refined motor oils. Besides Mobil One motor oils, I have a lot of experience with Red Line lubricants and oils and can strongly suggest either one. There are some other brands of synthetics promoted here on the forum that offer lots of test data to proove how good they are, but I do not know if they make any products in the viscosities that are usefull for engine life.

Good Luck!

 

Thanks for the responses. I use Mobile One 10w30 fully syn. as I live on the Gulf Coast and I never take my car out of my temp controlled garage if the temp is below 40 degrees as I am a firm believer that colder temps are not good on the paint, rubber and many other parts of my Corvette. If you do not believe this theory just call one of the family members of the Challenger Space Shuttle crew.

 

ttt

 

Don't even begin to believe the crap about piston slap. I have been around these motors since '97 and there has never been a reported failure of these LSx motors because of the "so called" piston slap. It is a buch of BS and the dumb azzhats that created the "Pistonslap.com" website should be piston slapped in the face. Anybody who knows anything about these motors will agree that they are the best small block ever put out by GM. Just drive the car and enjoy it.

 

Okaaaaay.....

 

LMAO, funniest thing I've heard all week. Do you plan on going 18000 miles an hour too?

 

Just a quick note, too.. LS2's make the same noise!

 

 

Additional comments:

Back in my Lotus days in the 70s, I had several custom built engines for my S2 Europa. There weire fitted with Arias custom made forged pistons, and they too slapped until they warmed up. Arias and my engine guys told me way back then that the strongest piston alloys have a higher rate of thermal expansion coefficent, so to fit right when hot, need to be a little loose when cold. This is exacly the condition in the LS engines too.

I agree that the LS1 and 2 are the best small block chevy ever produced. A lot of people are blowing or spraying these engines in stock form up to 500 or more HP and they still hold together. With stronger crank, rods, and pistons, and a bottom of block brace, they can hold 1000 or even more HP. Amazing for a production aluminum small block pattern

I still stand behind 20-50 weight oils, but at least you are not running that water weight crap. Just take it easy on the engine revs and loading until regular operating temps are reached and you should enjoy great service life. This is reasonable advice for any engine, not just LS engines.

 

O-RING?

If you had a bad O-ring in your oil pump you would really notice the tapping at cruising speeds, because it starves your lifters of oil. I know. Don't waste a butt ton of money looking into your $3 o-ring for a fix. Try a few of the other suggestions first, like the oil change.

If the car still has a stock oil pump and o-ring in it, that is highly not likely to be your problem area.

That is just my .02 cents worth.

Micah

 

I've had the dreaded piston slap since mine was new. It's got 53k miles on it now without a single problem.