Is it normal for the engine to have a slight quiet knock when it has sat for a week in my cold garage. I just noticed this and it seems to go away once oil temp hits 90 or 100. I never noticed it durning the summer. The oil life is at about 80% and I run high octane fuel so it should not be engine ping.
My wife’s Tahoe does the same thing and the dealer said this is just the way they are it is not doing any harm.

 

My 2004 5.3 Tahoe, 2007 5.3 Tahoe, 2008 6.0 Avalanche, 2009 Vette, 2011 Vette........have all been noisey. It concerned me for a year or two, now I don't even notice. Must be ok, never had a problem.

 

Thanks indyjack,
Are there others in the same boat or is it we just have sensitive hearing?

 

What exactly is the knocking and where does it come from? Will I feel it in the car? I'm guessing I don't have it but maybe I'm just use to it.

 

It sounds like a rod knock: it comes from the engine, you don't feel it in any way, and it increases with RPMs but seems to diminish as it the RPMs reach 3000. Once the oil warms up though it quietly goes away.

 

Piston slap??

 

Hey Mez, I have never heard piston slap before.
It seems to have a heavier sound I think than a piston might have. I’m just guessing.

 

My '05 does the same thing. Knock when it's cold, goes away after about 10 minutes. Do a search for engine knock.

 

yeah, sounds like piston slap...... which has been a problem with GM engines since the mid 90's (and several class action lawsuits).

My mom's Malibu sounds like a diesel in the cold weather till it warms up.

Here is a link to "what it is" FYI:

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

 

My first thought was piston slap. Maybe a bad lifter? Forgive me for being basic but do you know what a bad lifter sounds like? It's more of a tapping sound. I've never had piston slap with either my LS1, LS2 or LS7 but I've heard it in others. It's more of a faint knocking sound.

 

Thanks Guys,
I feel better it is not only mine with this. Wish it wasn’t so but that’s life. Thanks for the link lytmup, that seemed to cover both of my cars. I guess if it gets too loud I will just have to rebuild it and add more HP.
Got to find the positive spin right

 

JJC5, I think the lifter sound is a little higher pitched than a rod knock. I think it has to be the piston slap since both of my GM cars sound the same. I have never heard piston slap but it seems the most likely noise.

 

Check out THIS thread. This is what I read about it when mine started knocking.

 

[QUOTE=EVRose;1575991310]Check out THIS thread. This is what I read about it when mine started knocking.[/QUOT

After about 25k miles, I developed piston slap on the passenger side of my engine. The noise is identical to the audio link on the above posted link. GM service tech confirmed it, but at this time could do nothing.

I did some further research and found out that one of the causes of piston slap is carbon build up on the tops of the piston rings. I do not baby my car, so it is not from lugging around town and loading it up. One possibility of carbon buildup is an overly rich condition. The only modification I performed is an aftermarket air intake, but with the oem tune. There is a possibility that an overly rich fuel trims might of caused carbon build on my piston rings.

Remedy:

1. Installed my oem air intake and drove for 100 plus miles to make sure the ECM adjusted back to factory calibrations.
2. Added one 11 oz can of BG 44K power enhancer to about 12 gallons of gas and drove the car until I needed refueling. Results - 80% of the piston slap was gone.
3. Added a second 11oz treatment of BG 44k power enhancer to about 12 gallons of gas and drove the car until I needed refueling. Results - 100% of the piston slap noise is gone. Cold engine start ups are quiet, no knocking noise with only the fuel injectors ticking away normally, smoother idle and a happy 2008 corvette owner.

Since completing the BG 44K treatments has only been a month, I will know in time, if the piston slap returns with the oem air intake. At this time, I can only speculate that adding an aftermarket air intake without a tune might have caused carbon buildup on the rings resulting in piston slap or is it just the rich oem tune or a combination of the two?

I have no affiliation with BG products, but to this day it has worked for me!

 

My '07 LS2 has piston slap (loud enough for my wife to ask about) when cold. Dealer claims it is normal. Unfortunately the service manager said it occurs before forged pistons expand, it is unfortunate because LS2 is not forged piston, they are hypereutectic, but he is on the right track. He said it is a common complaint with LS2 motors, and not to worry. To me it means the at least one of my pistons has extra clearance before it gets warm. Guess it is a good idea to warm these babies up before going WOT?

 

Keep it an eye on it, probably not an issue. I know I get some lifter noise after the car has been sitting a while, lasts about .5 to 1 second and goes away as the pressure builds up.

 

I also have had a slight knocking noise that lasts for about 1 - 2 miles from a cold start and then goes away. I bought a 2008 ZHZ with 31k miles and now have 51k miles and the noise has not got worse (or better). I thought it was a stuck lifter but after reading Mike's LS3 experience I decided to try the performance improver BK44. This is something that I would never normally try as most of the performance improvers seem to be worthless snake oil. Anyway, I put two bottles in the gas tank and added 15.8 gallons of gas. I am now down to about 1/4 of a tank left and the noise has all but disappeared! If you know what to listen for you can still hear it but it is just barely audible and still goes away after a couple of miles. It will be interesting to see if it comes back at all. Hopefully the BK44 works as advertised and does not harm the fuel system seals etc.

Thanks for posting this thread - good suggestion that worked for me.

 

Did you put 1 or 2 bottles of BG 44k in one tank of gas? It would be more beneficial, if you added one can to about 12 gallons of gas and drove for a longer period of time, using two tankfuls of BG 44k vs. two cans in one tank. However, it does seem like your piston knock has improved and is related to carbon deposits rather than lose engine tolerances. The BG 44k will not help piston knock or slap due to lose engine tolerances.

It has been 6 weeks since my two treatments with BG 44k and no more knocking.

 

Mike,
Yes, I put two bottles in the tank and filled it, so I had it mixed with about 18 gals of gas. I did think about one bottle per tank of gas but as I recall the instructions were to add one bottle in up to 12 gallons of gas so I could either add less gas or more additive (I do not have the instructions now, this could be wrong). Fortunately it seems to have worked. The first time after adding BK44 I drove it for only about 10 miles and the next day there was an obvious improvement. Since then there have been a several 25+ miles trips and a few full throttle accelerations after warming up. It must be my imagination, but the one today seemed to accelerate faster and the NPP exhaust seemed louder. It was 36 F here (SC) today which probably impacted the performance more than the BK44. Either way, can't wait for the weather to improve a little and take a run to the coast for a day or two.

 

I posted about lifter noise when I started the car one morning. With some help from forum members I found the problem was due to the oil filter. Symptons:
1. slightly low oil pressure
2. oil looked a little frothy

Suggest change oil and use different filter and see if any improvement.

Question forum members: Could air get in oil if filter not tight?