I have a 1984 FJ60 with 1HDT Diesel Engine and H55 transmission. When I first acquired the rig, it seemed to run hot; on a long hill it would go from 175 F to 215F. I replaced the thermostat with a new one (175F) and put in a new high capacity (375 HP capable) radiator and a 4000 CFM dual electric fan. This doesn't seem to have made much of a difference; on a long hill, it'll still go from 175F to 205F. I can't put any higher capacity radiator or fan in, so I'm kind of at a loss as to what's going on. I had this same radiator and fan in my 355 hp, V8 powered '82 Landcruiser, and it never overheated. The 1HDT only makes 167 h.p., so I'm a bit confused. P.S. - it doesn't use any coolant, so there's no head gasket issue.