Repeated failure of round gasket / ticking or hissing noise.
Spring Bolts Failure
Spring bolt kits maintain constant pressure on thick gaskets while compensating for wear due to movement between adjoining pipes. With age the springs loose tension and sometime break due to rust.
Replace failed spring bolt kits as an assembly and replace worn corresponding gasket. Also inspect motor and transmission mounts for excessive movement which can result in excessive exhaust system articulation. Replace worn engine and transmission mounts as required. Caution: Spring bolt kits use shouldered bolts which can break off at the turned down section if over-torqued or during removal if heavily rusted. If bolt will not turn try using penetrating oil to break the rust. Another method would be to heat the bolt (red hot) followed by quenching with cold water.