2000 Malibu Piston Slap?

[Fishinguy40]

Here's another Malibu issue, 3.1 Liter, 116K miles.

Son borrowed the Malibu for a couple weeks. He called last night and said there is a loud "knock". He thought a rod or a valve. I went over today and listened to it. I'm guessing it's a piston and not a rod or valve because it is loud and sounds like whatever it is has some mass to it. It isn't the typical high pitched clacking or ticking but more of a deep clunk. You can also feel it. Car runs great except it sounds like a piston is going to go through the block. I didn't drive it. I was afraid to.

Does this sound like piston slap? Could there really be that much clearance between the piston and cylinder walls to cause it to slap/knock that loud but still run smooth?

I'm assuming that the car is junk.

[Macgyver55]

Piston slap normally goes away shortly after the car is started, as soon as things start to warm up it fades away. If you have a knock beyond that it may be more serious. How does the oil look?

Has the car had intake gaskets in the recent past, or has it ever had antifreeze in the oil to your knowledge?

[Fishinguy40]

Here is a link to a video of the engine running. The loud whine you hear is a rebuilt power steering pump. Benn noisy as heck since I put it in a year ago.

The "slap" did seem to guiet down after the engine ran for a few minutes but would come back when you give it gas.

I replaced the lower intake manifold gasket myself several years ago and have not had any issue since.

Piston Slap?