I just had to replace an oxygen sensor in my 2000 Honda Civic LX and upon the mechanic replacing the sensor they discovered a crack in the exhaust manifold. I know that this year and model Civic has had issues with the exhaust manifold cracking but my car has 106,000 miles on it so it's not covered. The crack actually originates from the hole the sensor is screwed into so I have some suspicions as to whether the removal of the bad sensor caused the crack. In any case, is it possible to weld a crack on an exhaust manifold or is that just not done? If it is done, how long could I expect the weld to hold?