1994 Ford F Super Duty 460 problem
 

I'm in the process of putting new exhaust manifolds on my farm truck. Tonight I was getting ready to install the drivers side and noticed that the dipstick tube was loose at the oil pan. Upon further inspection I noticed that the previous owner had siliconed the dipstick in place. The pan was a obvious spot for it. There is a o-ring on the bottom of the tube where it goes in the pan. I went to Oreilly's thinking maybe the oring was bad. They can not find anything on saying that this should be a pan mounted dipstick tube. Does anyone have any information to help me out??