Is this sound under the bonnet normal?

[Lexusrx350guy]

 

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My mechanic says it's normal in a chain driven engine but I'm not convinced. It's just annoying more than anything. I recently changed the engine belt as well but it  doesn't seem to help either

[Ashley]

Does sound a bit noisy my 05' GS 300 timing chain rattles for 1-2 seconds when cold upon start up however, this only happens 1 in 15 to 20 cold starts. I checked with Lexus and was told its just a second before the oil pressure builds and gets to the top end which makes sense. Another noise which you may have on your car is a clicking sound coming from the back LHS of the engine I believe this is a fuel sender unit however don't quote me on that. 

I have never had any error codes and my car runs like a dream. 

 

Regards.