As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
HYD 2 OVR TEMP MSG. RAN QRH SAW 100 DEGRESS C AND PSI OF 3100. ROUGHLY 30 MINUTES LATER HYD 2 HI TEMP EICAS MESSAGE REAPPEARED EXACTLY ONE MINUTE LATER HYD 2 OVERHEAT EICAS MESSAGE SAW TEMP PEAK AT 200 DEGREES C AND PSI WAS ZERO RAN QRH EHG PUMP SHUTOFF WAS PRESSED TEMPS REMAINED CONSTANTLY HIGH AND LASTED ROUGHLY 15-20 MINUTES DECLARED EMERGENCY COMPLIED WITH THE EMERGENCY CHECK LISTS LANDED-C/A-REMOVED AND REPLACED #2 HYD SYS HEAT EXCHANGER THERMAL BY-PASS VALVE PER EMB-170 MM 29-11-14 OPS AND LEAK CHECK GOOD AT THIS TIME