Originally Posted by Dudewanarace

My 2001 4.4i had an alternator failure at about 90K miles I think. It just stopped charging, no leaks. So, that being said, there is some merit in replacing it while your there.

But, like others have said, I wouldn't think the O-ring would be the leak. It is more likely the coolant supply line that comes out of the top of the alternator housing and T's in to the upper radiator hose. I bet this was removed while doing your timing cover gaskets and either wasn't seated properly, or the O-ring in that connection is old and not sealing. There isn't a return line, as it vents the coolant back through the timing cover to the water pump cavity. Err maybe it goes the other way. Pump to alternator to external line to upper radiator hose. Not sure, but doesn't matter.

Hell, last time I had my alternator out I didn't even replace the main O-ring, just re-used it and it is working fine so I doubt that is your problem.