which was on a 89 honda prelude which was my DD and after about 2 yrs the header developed a leak at the collector. After investigating i learned that the header had crystalized at the collector were the 4 meet the 2. That area became so brittle that tapping it with a socket extension caused it to shatter my guess was that the heat that was trapped in the header while the engine was off had no place to desipate to quick enough causing the metal to crystalize. It did great job of keep the heat down off the hood.