Re: 2005 5.4 f 250 leaking coolant off oil filter
If the block is rusted, the freeze plug may have been compromised by a previous owner who neglected it for a period of time (parked it outside in winter without proper coolant/water mix, etc). If the mix isn't right, when the water freezes the plug will expand taking pressure off the block itself. I'd remove the freeze plug (coolant will come out!) and install a new one. I think I had to hammer the last one in and seal it if I'm not mistaken on my older Dodge; but that was 12 years ago. I had to remove the exhaust manifold to gain access but I saved myself $150 in labour costs at the shop. Ran great after for two more years before I traded up for my Durango R/T.
One thing you can try to be certain it's the freeze plug area. Is buy some UV dye, and add a bit to the coolant; drive the vehicle and with a UV bulb, you'll notice the source of the leak as it'll stand out.
'11 Ram Quad Cab 4x4 SXT 5.7L HEMI (stock); 48,500m
'06 Pontiac G6 GT 3.5L 220hp; 64,000m
'12 Chrysler 200 Limited 3.6L 283hp; 28,000m
'99 Taurus 3.0L 2V Vulcan 145hp; 154,300m - Traded
Amsoil in all vehicles!