The man speaks the truth - get it checked. A pressure test should pinpoint the leak. I had a small leak (about a cup every 10 days or so) when I bought my '95. For awhile I just topped it off then last Nov I dumped some Prestone Stop Leak in it. This worked for awhile but after finding a puddle of coolant Monday after warming it up I finally took it to a radiator shop to get it pressure tested. It was leaking on the driver's side near the bottom of the end tank.
Pulled it and besides the obvious corrosion in the last 4-5 rows there was a buildup of sludge from what I'm assuming was the "stop leak".
New radiator - $168, hoses & clamps - $43, flush, antifreeze & labor - $157 (had them flush it to make sure as much of the stop leak crap was removed from the system as possible)
The stop leak may or may not have done more harm than good, I don't know. At best it's only a temporary fix.
From looking at my Chilton's I'm about 99% sure my Dad & I could've replaced it ourselves but spending 3 hrs in a non-heated garage in below zero weather just really didn't appeal to me Monday.
