My Series 3 utility overheats under load, could.

My series 3 utility overheats under load, could this be symtoms of leaking head gasket into water jacket, or maybe restricted passage size in water jacket. Thermo fans are operating. Have installed seperate transmission oil cooler. Come to think of it, it is lacking power. The car seems to be allowing eccessive fuel through the exaust on start up and milege per tank is getting less. Any ideas?