Knocking Sound - Hammer on nail

[BMWDemon]

Hey guys, Started noticing a sound from the engine. When the car is idling (with the hood up) as the compressor kicks in, there is a single knock sound. Similar to knocking a nail with hammer. Any you guys had similar experience ? Havent heard this sound before.

 

[B33mEr]

Compressor ... what compressor bro? aircond? Can take video of the engine when making this sound?

 

[BMWDemon]

Aircond Compressor bro. I tried the video thingy, but combination of bad phone speaker and growl from the 3 liter engine muffles the knocking sound when recording.

 

[aidilj]

So the sound of the hammer is only once, as the compressor clutch engaged. not continuous as long as the clutch is engaged?

edit: just read your post again, its one knock

 

[BMWDemon]

Aidilj,

U are right. Only once, but everytime the compressor cluth engages. Not continuous.