Piston slap and Belt slap

[ueberooo]

how do you distinguish these two sources of sound?? Are they often confused? I don't know how to tell them apart.

I've watched a whole bunch of youtube videos on pistons slap and I still don't know; though, after I tried to tape the engine sound from the cabin with my camera (in video mode) and listed to the recording, I noticed the sound quality is such junk those fainter noises are completely lost in the audio.

So, as for my car, I'm not sure what sort of sound I'm hearing at lower idle like speeds, but I believe it's more likely coming from the belt. The tension is such that at the low rpm it seems to have some sort of resonance going to make a regular slapping sound. Is this likely right?

 

[BoomerCTD]

I would remove the serpentine belt, and run the engine briefly to see if the noise goes away, that should eliminate any belt noise.
Mike

 

[willix]

Pouring water on a noisey belt will quiet it instantly.

 

[dailydriver]

Is the tensioner a crazy expensive/impossible to reach item on the Scoobies??

If not, maybe just replace it (especially if it is the original 175K mile piece anyway)?

 

[mechtech2]

I'd take the belt off, too.
this will quickly determine if it is engine or accessory, pulley, tensioner, or belt noise.

 

[ueberooo]

Well, it's due for a timing belt change pretty soon... in 5k or so; so I'll ask the mech if it's advisable to change out the original tensioner and any other parts.

IMO it isn't an excessive noise; just noticeable as some sort of low idle speed slap noise; not terribly loud, and I actually don't mind the sound and it's been around for years, possibly as far back as I've owned the car (got it around 115k ish?--but I didn't pay attention to the detail of the engine sounds of the car back then).

 

[meep]

tensioner on this car is on the TB, it's hydraulic/spring unit. requires TB removal. My 2.2L bearings were shot at 100k.

the serpentine uses a bolt-tensioned pulley near the PS pump IIRC. totally different tensioner.

M

 

[CBR.worm]

In my experience piston slap makes an engine sound like a diesel - sometimes only when cold.