If the person before you owned it, screwed in the stud on a stud that went into a water jacket. Without using a sealer on the threads.
( Sealer usually used is permatex gasket black or red sealer on the threads. Water-oil-heat proof. ) Eventually the coolant will seep thru the threads and pit where the bold and threads meet.
JB is a good thing for as JohnW and Radnack said. On the face where the gasket seats. Put it on and scrape with a razor blade and go a little higher to use a wood block later when dry with 120 grit sand paper to finish it flat.
On the threads, do the same with JB. Coat the stud with it, screw it in, let cure 24 hrs? Back it out. Then re-install with permatex on the threads. By the by, to take out a stud. Double nut it. Take the original nut off, go to the hardware store to get a exact replacement, thread size. Put the original nut on, the 2nd nut goes on next. Over the original. Hold the 2nd nut firm, wrench on the original and back the 1st nut off to bind against the 2nd nut. Wrench on the top nut to back it out.
On the JB, I replaced the intake manifold gaskets on my 2003 Sonoma truck with the 4.3 V6. Long and short, originals were plastic body's with plastic seals around the intake holes. New gaskets were from Fel-Pro. Metal body with rubber seals around the intakes on the head. The heads had a lot of pitting around the intake ports. JB weld, I smeared JB over all of it. Little higher using my razor blade.
220 grit sand paper over a wood block, back and forth with a figure 8 pattern. 100,000 miles later still good to go. Yuppers I've owned for quite a few years.