In the case in which the motor makkes a noise (knock or rattle) after the timing chain has been replaced or after replacing the water pump, it is possible that the culprit is the hydraulic tensioner for the GM 2.4 liter DOHC engine.
Why does this occur?
If you did a "reset" of the hydraulic tensioner and installed it, see if you can remeber it being depressed and the chain lose in that area. You might remember thinking that once the motor starts, the oil should pop it out. If this is your case, guess what... it will never happen. You need to complete the reset and this is easier said than done.
How do you correct his?
You need to get acess the tensioner again, meaning you need to remove everything you did until you can get the timinf cover off. I recommend that you do this by lowring the motor and from the wheel area. I also recommend a screwdriver since it worked for me.
With the flat part of the screwdriver press down on the plunger. If you recall, you did the reset by pressing on it until it went no further. Actually it does go in further and this is what we need to do. Leverage the screwdriver to press the plunger in and keep on until you noticed it went in more (normal) and keep on and if you feel or hear a click, release the screwdriver. If you don't hear anything try you luck and release it. Once you have pressed it far enough, it will release the spring tension and you are set. Believe me you will have a smile by then.
Did it work for me?
It sure did and no more knock or rattle...
End of mym story!!!!