Knock, knock, knock (Who's there?)

[wmorrison65]

A few minutes after I start driving (when the engine is cold,) I hear a faint "knock, knock, knock" sound. Always three, same even spacing. Can't tell where it's coming from. I assume since it's consistent that it's something normal, but I'm curious what it is.

'01 GTP

[Scottydoggs]

if it goes away its kinda normal, its a lifter is loosing pressure when it sits over night. oil change used to stop it on my car. if it started to tap, i knew i was over due for sure lol

[Slick2500]

Sometimes running some seafoam in the oil for like 50-100 miles before an oil change will help.

[wmorrison65]

if it goes away its kinda normal, its a lifter is loosing pressure when it sits over night. oil change used to stop it on my car. if it started to tap, i knew i was over due for sure lol

It doesn't sound like that. It sounds like a solenoid or something it being triggered. There are always exactly three knocks, and they are always spaced exactly apart by the same amount of time regardless of engine RPM.

It's quiet enough that if you had the radio on, and/or were already driving fast enough for engine/road noise, you probably wouldn't hear it.

And I just had an oil change within the past month.

[BillBoost37]

Wes...you know my feeling, the radio can always go louder.

[wmorrison65]

I tried recording it this morning, with my phone on the dashboard. I heard it "live," but can't hear it in the recording. Tonight I'll edit the audio file and press the "enhance" button several times.

Again, I don't think it's a problem, I'm just curious what it is. Wondering if it's related to some emissions equipment that doesn't "kick in" until the engine has warmed up a little bit.

[industrialfish]

Don't worry, my 05 does it too, so did my 01 Firebird. Pretty sure it's something to do with the evap canister solenoid or something.

[mkyota1]

My 04 deville does it too. Weird. Normally 3 or 4 mins after cold start.

[Fivefingerdeathpunch]

I'd say it's the EVAP solenoid.

My silverado did it too but I could only hear it when it used the remote start and I was standing beside it.

[nos4blood70]

My Bonne does this occasionally as well, sounds like it's coming from the back.

[GOGOPONTIAC]

I used to have a 98 Grand AM that did 3 quick little knocks that sounded like it was coming from the back. Did not have to be certain temp it would do it at a light after driving awhile or sometimes soon after startup.