As was mentioned .. Studs going into open holes have to have a sealant on them. I have always used Loctite # 582 teflon sealer and never had a problem.
If you dont want to remove each stud and apply the sealer to them, get some K & W Block Seal or Moroso Ceramic Seal and use as directed.... both will seal up the leaks for a year or so .. or permantly.