I have a 2005 honda civic cvt..?

i noticed today while i while in my drivway the engine was making this slight but noticable rattle..only when in drive or reverse then the engine was a little louder than normal while driving but later on in the day when i drove it again it wasnt rattling..im brining it in to the dealer on tues because of an ongoing break problem...the brakes creak..and they told me 3 times it was nothing!! but another machanic told me different so while im there for that i will have them check the engine but any ideas on what it could be?