i noticed today that i am starting to get oil in my antifreeze.my oil is fine no antifreeze in it.and when you take the cap off of radiator there is a little pressure coming out after the cap has been off a while.so is it a headgasket or maybe timing chain that put a hole in the cover? also starting to get a knocking sound could this have to do with antifreeze problem?mite need to pull a rebuild the whole motor?or maybe just head gasket and timing chain?any info would be appreciated