As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HEAT EXCHANGER SIDE PLATE HAD FOUR CRACKS ABOUT .35 INCH LONG. THE OPPOSITE SIDE OF THE HEAT EXCHANGER WAS CRACKED IN FOUR OF THE FOUR CORNERS. A NEW HEAT EXCHANGER WAS INSTALLED. PREFORMED A LEAK CHECK ON THE DEFECTIVE UNIT AND FOUND THE CRACKS EXTENDED INTO THE COOLING FIN AREA, WHERE THEY CAN NOT BE SEEN.