THE RD 800 SERIES MACK TANDEM WAS TRAVELING FROMTHE HIGH WALL MINER PIT TO PREPARATION PLANT DUMPSITE. THE DRIVER STATED THAT HE HEARD A POP NOISE UNER THE HOOD, HE THEN STOPPED TO CHECK THE T RUCK, TRUCK WAS ON FIRE UNDER THE HOOD,FLAMES WERE COMING THROUGH THE DASH FIREWALL AREA. SAFETYCREW WAS CALLED AND FIRE WAS CONTAINED:PROBABLE CAUSE:LINE BLOWN SPRAYING OIL IN TURBO.