I have a 97 Rav4 with 15k on a rebuild (2L4 cylinder) Have always used quality 10w-30 and Toyota filters. If the car has sat for 24 hours, it will rattle on start-up like I have a loose rod bearing. After a couple of seconds and the oil pressure light goes out, the rattling stops and the engine sounds as if I would expect. If I stop and start it again within a few minutes or a couple of hours, it will sound normal at start up. But if it is allowed sit for several hours or over night, it will rattle on start up. Any ideas why? I believe the filter has a leak down valve in the filter. And the filter sits on top of an oil cooler. I suspected pre-maturely failed bearings or pump but am now thinking maybe it may be something else. Any ideas would be appreciated.