Toyota 2009 corolla S, it has been making a strange noise. i have my belt tight on 2009 Toyota Corolla

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Toyota 2009 corolla S, it has been making a strange noise. i have my belt tightened it was loose and it is tight and it is still making sounds like for the first five seconds after it's been sitting for five hours or overnight remakes it,the sound that it makes is that of beating wood with a hammer really fast for like five seconds then it goes away doesn't come back until gets cold again. Cold meaning not driven 5 plus hours. And all this started after they replaced my water pump. I'm running 0w-20 oil is what the car calls for. My hunch is the chain tensioner.
(2) Answers
I was told that this is due to some little device that flips the oil up when you first start the car, and because there is no oil in it when you first start the car, it makes that awful noise. I am disappointed that this happens but there is no fix for it. I also run the 0W-20 oil and it still does it. I have also been told that it will not harm your car... but I don't know. Every time I start my 2009 Corolla LE I cringe at that noise...
most likely tension arm. had similar prob. turned out to be tension arm and the steering pump. i changed them both, prob. solved. may want to change the belt all together(goodyear gatergrip). they are like tires. their grip wears out with time. try the belt first(cheap and easy).