TransAmBlue

I bought a used 01 WS6 with 38k miles on it from a Chevy dealer. Runs good and looks like it was well taken care of. The problem is the engine knocks at idle hot in gear. If are sitting idling in drive you can hear constant knocking, bump it out of gear or give it a little throttle and it stops knocking.

The oil is perfectly clean and the car runs like new, doesn't seem to use any oil. How can I tell if its piston noise or bearings? These LS1 engines are so dam hard to diagnose, I've owned 4 LS1 cars and all made some knocking but this one is different. If you put it in park and open the hood and listen its dead quiet....rev it quick dead quiet.

I hate to go back to the dealer because usually I know ALOT more about it than the techs doing the diagnoses.

JRENIGAR

iTrader: (37)

If its an auto (and I assume it is) then its probably a cracked flywheel. It sounds just like a rod knocking and usually dosent do it when cold or not under a load. If it was a rod knocking it would do it hot or cold and in or out of gear wouldnt make any difference. Post back results.

JRENIGAR

iTrader: (37)

It might also be loose converter bolt hitting the back of engine. Remove the starter and use a screwdriver to rotate the flywheel to gain acess to the bolts and also look for a crack or cracks inbetween the crank bolt holes and the big holes in the flywheel while your at it. I actually have had both of these happen to me due to previous owner not knowing what he was doing. If its converter bolts use some blue locktite. If its cracked flywheel, well, you can imagine whats next.

TransAmBlue

I'm taking it back to the dealer and have them check the flywheel and convertor bolts. But i think its a case of severe piston slap. If I idle and get the engine very very hot the noise almost goes away. I had the oil changed and it was clean, no metal etc. so its not anything coming apart. I've heard of extreme caes of piston slap before.