When ever I start my Yukon after its been sitting for at least 2 hours, there's a loud rattle which sounds like its coming from above the front passenger tire by the firewall. It only last a second or 2 and stops and does not do it on start up again until its been sitting for a while. I thought it might be some loose ac hoses, those are all intact. I put rubber in between the hoses that are real close to each other to see if that might be them bumping on start up, but that's not it. My oil is clean, I replaced all the ac hoses in it at the end of last summer but it was doing this before I changed them and still making the noise. Any help would be appreciated on what it might could be.