Just another update. Today found another truck leaking at o ring with 3200 hours on the clock. When removed they do not seem hard and are still pliable. When replaced , I use sealant on o ring. Never leak again. Do not seem to fit tight in housing and possible vibration/ movement may be issue. Also spotted another water pump leaking today at 2850 hours. Think this may be caused by not being able to adjust belt tension..stretch belt too tight and taking out pump bearing. At least I know where the coolants been going!!!