My Cadillac is making a knocking noise under the hood. What could it be?

[nightwalker ^..^]

could be the air pump , could be the harmonic balence , or could be a pistons going bad , take it to tech and theyll pin point it exactly

 

[dimeback]

bad head or piston- trade it in for a new one.

 

[Nicole]

I thought it was the oil pump so i replaced it, but that was not it.

 

[dimeback]

bad head or piston- trade it in for a new one.