The Ws6 I just bought with 38k miles on it has a funky claky noise in the engine all the time. Cold its really bad and after it warms up you only hear it at a idle stopped in gear. Bump it out of gear and its gone. Anyone have some experience with piston slap noises?

I thought maybe loose flywheel bolts or Tq convertor bolts but why would the noise get less the hotter it gets if they were loose.

I'm gonna take it back to the dealer and have them check it but i'm sutre i'll get nothing but BS from them.

 

Post up a video if youre really curious. But it's probably just normal piston slap. Out of the many ls1 cars I've heard only a select few have been quiet all the others had piston slap when cold and when warm

 

It's normal, both of my ls1 cars do it, even warmed up a little.

 

Thanks for the replies. I don't think it would record well enough to be heard.

The way sounds I think the flex plate is cracked, only knocks in gear at a idle and sometimes it will clatter as you put it in gear. Guess I'll know wed when the dealer looks at it.

 

Take off the inspection cover and look at it yourself

 

Impossible for me to do that. I think there maybe a problem with the engine oil pressure. Seems the the longer you drive it the noise gets worse and maybe its the lifters i'm hearing making this clattering sound at idle. Its very hard to describe, If i let idle out of gear its quiet and put it in gear it stays quiet till you drive it a bit. Then when you come to a stop its clattering like hell.

Its freakin me out how such a perfect looking car and trust me someone was **** about caring for this car could sound so bad. Oil is perfectly clean and it runs like a new car except this dam weird noise. It almost sounds like piston slap BUT no matter how hot i get it it never goes away. Plus the oil pressure gauge acts strange at times, It will be at 40 at idle in gear and suddenly drop to 38 then 42 back and forth.
At theSame time the engine has a slight miss to go along with this gauge movement. Also driving on the highway the hotter it gets the oil pressure gauge starts to seem lazy and doesn't move quickly. The oil pressure is good 40-65 but lazy to rise when the engine is good and hot. At times its a minor sounding tick but at times its knocking loud enough to hear it in traffic.


When I test drove it at the dealer I didn't hear anything like this but I only drove it for about 1/2 hr or so. Seems its ok for that long of a drive then all this craziness starts.

I've owned 4 of these cars but never experienced anything like this. If it is the oring leaking will it damage anything?

I know this all sounds complicated, not sure what i'm dealing with at this point. Maybe a bad oil pickup oring? Unfortueatly I can't do any kind of work on the car.


Any suggestions would be helpful. Thanks

 

Post a video.

 

Well today what I did was drive it around and listen carefully, seems if I drive up a long grade where the engine gets good and hot the noise disappears. Then as you drive on the flat again and it cools down a bit back it comes. Guess its a sure bet its piston noise but dam its loud at a idle. On the gas you don't hear it.

 

FWIW I had the same symptoms you explained, it was horrendously loud when cold and very quiet once the engine warmed up. Took it all apart since I was going to build it anyway and #7 pistons had some super wear on the skirts compared to the rest. Wrist pin was slightly looser compared to the rest. W would check the valvetrain first before condemning anything and tearing it all apart.

 

Yep i'm guessing something like that, I'm going to unload each cylinder till I find which one is knocking. If it turns out to be 7 its a sure bet the piston is damaged. No 7 takes a beating and runs hotter because of the intake design.

I'm really curious how the dealer is going to handle this.

 

I had an ls1 car do this exact thing. Sounded just like a rod knocking. My money says flex plate cracked or bolts are loose hitting the back of the block.

 

Well before the dealer looks at it I have to say it seems to be severe piston noise. I've found if I run the engine hard for a few miles the noise almost completely disappears, then starts coming back as you drive normal. One other thing is the engine is completely stock as far as I can tell but it runs fantastic. It has great power and pickup that my other 4 "quiet" LS1 cars didn't have.

Maybe Pontiac built these WS6 motors looser than the rest for more power. I don't care how it sounds as long as it lasts.

 

Seafoam the engine after its warm. Wait for it to soak for about 30 minutes before starting the car again. Have a or a , whatever your preference. Start the car and prepare to have your neighbors hate you for 10 minutes or so while it burns out the exhaust. I have found that this completely eliminated what I thought was piston slap in both my ls cars. You might still have a cracked flywheel and it just sounds like a knock in the engine because of the harmonic knocking sound it sends throught the flywheel and out the rods and pistons. I had to be shown that it wasnt a rod knocking on my car to believe it. My dad has been working on cars for 50yrs and once again the teacher showed the student why he holds that title. Im not the teacher now but I have taken his class. Constructive criticisim is a good thing my friend.

 

Did you only hear it in gear at idle?

 

Sometimes yes and no. Its flexing because of load put on the verter causing the crack to flex back and fourth. This is where the sound would come from.

 

I'm sure i have a couple different issues, 1 is piston slap cold and 2 is rod bearing noise once its warmed up. The engine oil pressure acts very odd at idle and the knock i'm hearing follows the shaking of the oil pressure gauge. PPutting it in gear just lowers the rpms and thats when you will hear worn rod bearings knocking. Also If I drive it hard every time it shifts the engine has a definate rattle sound<typical of worn rod bearings.

I'm going to try annd force the dealer to refund the deal, I've had enough of the bs.

Unfortueatly as great as this car looks it must of had a tough 38k miles. Strange because its so clean, even the oil.

 

well yeah, there is that.

 

Weird thing about all this is while you are stopped in gear with the engine idling making this funky knocking noise all you have to do is give it a slight amount of throttle and its gone. OR take it out of gear.....its just baffling the crap outta me.

I did ALOT of looking on the net on this subject and found Toyota has ALOT of trouble like this. Knocking in gear ar idle, they claim its wrist pins. I also found other info on bearings both rod and mains, looks like i'm ok there. Rod bearings would continue to knock as rpm changed and mains would cause low oil pressure.

So once the flex plate is checked out its a safe bet its piston-wrist pin noise.

I'm sure the reason I never heard this when I test drove it the temp was around 40, Its been in the teens and 20's ever since I bought it. Dam cars sure are a PITA!

GM needs to get its **** together!

 

my buddy's car had symptoms like this and it was a motor mount. but his car had 160k miles it too.

both of my lsjuan cars had what I think is piston slap. this ta did it at 36k and now has 113k on it and really nothing has changed. loading the car causes a knock that's not good.

 

I've had multiple trucks (2002 6.0 liler,2004 4.8 liter, and 2007 5.3) that had piston slap. I've fought Chevrolet over it until I was blue in the face, and they finally extended my drive train warranty to 100K miles. Regardless, piston slap is unfortunately very common in the LS engines. I've hear some that have it worse than others and some not at all. Just accept it as part of life. Sorry I couldn't be more optimistic for you.