I can't say I've ever done that but for sure you'll have to start with removing the lower hose and looking with a lamp and mirror. If your radiator has a built in transmission oil cooler (whether stick shift or automatic) the cooler tube may keep the seal from dropping to the bottom - or the seal could be stuck at the cooler tube altogether. If the seal isn't at the bottom you'll need to remove the radiator and shake it around to get the seal near an opening (top or bottom) and use a pair of needle nose pliers to fish it out. Have another new one on hand. -- Dave