As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON INSTALLATION OF NEW NR 4 EXHAUST PIPE, THE FLANGE WELD BEGAN TO CRACK. THIS WAS WITH LITTLE TORQUE APPLIED THE FLANGE. SUBMITTED REPORT TO MFG AND DISCUSSED WHAT MAY POSSIBLY BE CAUSING THIS PROBLEM. THEY SEEMED TO THINK IT WAS THE USE OF MFG EXHAUST GASKET WITH THE ASBESTOS CENTER CAUSING THE PROBLEMS, THIS IS THE SAME GASKET THAT IS CALLED FOR IN THEIR PARTS MANUAL. THEY RECOMMENDED USING TWO THIN COPPER GASKETS INSTEAD OF THE SINGLE THICKER ASBESTOS/COPPER GASKET.