CL65 FLT CREW HAS A LNDG GEAR OVERHEAT WARNING WHILE ENRTE; DECLARES AN EMER AND DIVERTS TO CMH.

Narrative

IN CRUISE ENRTE FROM CAK TO CVG AT FL200 PASSING OVER CMH; THE 'GEAR BAY OVERHEAT' AURAL; THE TRIPLE CHIME AND MAIN LNDG GEAR BAY OVERHEAT WARNING MESSAGE APPEARED. THE FO BEGAN TO SLOW THE ACFT TO 250 KTS; WHILE I RETRIEVED THE QRH. AT 250 KTS THE GEAR WAS LOWERED AND HAVING COMPLETED THE MEMORY ITEMS FOR A MAIN LNDG GEAR BAY OVERHEAT MESSAGE I CONSULTED THE QRH. AS THE MESSAGE REMAINED ON THE EICAS; THE QRH LED TO 'LAND AT NEAREST SUITABLE ARPT.' AT WHICH POINT I CONTACTED ATC; ADVISED THEM OF THE EMER AND OUR INTENT TO LAND AT CMH. WE WERE IMMEDIATELY CLRED TO CMH VIA RADAR VECTORS; STARTING WITH A L TURN AND GIVEN A DSCNT TO 11000 FT. THE FO BEGAN THE DSCNT. WE NOTIFIED THE FLT ATTENDANT; I CALLED DISPATCH UTILIZING COMPANY RADIO; AND DISPATCH NOTIFIED THE COLUMBUS STATION OF OUR ARR. I THEN MADE A BRIEF PA TO THE PAX EXPLAINING THE UNPLANNED LNDG IN COLUMBUS. WE WERE BEGINNING THE APCH FOR RWY 28L IN COLUMBUS WITHIN ABOUT 5 MINS OF DECLARING THE EMER. ON DOWNWIND FOR THE APCH; HOWEVER; THE MAIN LNDG GEAR BAY OVERHEAT WARNING MESSAGE HAD EXTINGUISHED AND WAS REPLACED BY THE MAIN LNDG GEAR OVERHEAT FAIL CAUTION MESSAGE. DURING OUR ARR INTO COLUMBUS; WE DID EXPLAIN THAT WE HAD SOME DOUBT THAT THE WARNING WAS A LEGITIMATE ONE AS THE SYS HAD JUST BEEN REPLACED BY MAINT IN CAK DELAYING OUR DEP FOR 4 HRS OR SO. THE BRAKE TEMP MONITORING SYS ALSO INDICATED 01 01 01 01 (01 FOR EACH MAIN GEAR BRAKE; A COOL INDICATION). THIS INDICATION WAS NOTED IMMEDIATELY UPON LOWERING THE GEAR; INDICATING THAT THERE WAS PROBABLY NO OVERHEAT. THE FACT THAT THE WARNING MESSAGE HAD ALSO GONE TO A 'FAIL' CAUTION MESSAGE BY LNDG INDICATED THAT THE SYS MAY HAVE BEEN FAULTY. I ALSO GAVE A FINAL CALL TO THE FLT ATTENDANT ON FINAL; TO MAKE SURE THAT SHE WAS COMFORTABLE AND LET HER KNOW THAT SHE NEED NOT BRACE; AS I WAS UNSURE IF WE DISCUSSED IT EARLIER IN THE FAST PACE OF THE INITIAL DSCNT. I ALSO TOLD HER THAT THE EMER VEHICLES WERE STANDING BY BUT WE REALLY DIDN'T EXPECT TO NEED THEM (REASONING THAT THE SYS WAS PROBABLY FAULTY; AS IT HAD BEEN WORKED ON FOR HRS. THE BRAKE TEMP MONITORING SYS WERE ALL IN THE GREEN EVEN WITH THE OVERHEAT WARNING AND THAT AT THIS POINT THE WARNING WAS GONE AND A CAUTION INDICATING A SYS FAILURE WAS ALL THAT REMAINED). I ELECTED TO TAXI TO THE GATE UPON LNDG WHILE THE EMER VEHICLE FOLLOWED; RATHER THAN HAVE THEN INSPECT THE ACFT ON OR JUST CLRING THE RWY. THEY FOLLOWED US TO THE GATE; WHERE THE INSPECTION YIELDED NO ABNORMAL INDICATIONS.