I seem to have a cooling problem. My range rover classic recently had a beautiful new top-hatted 4.6 built for it, and with that went a new airtex water pump, all new hoses, and a new thermostat. The radiator was replaced a few years ago with an inexpensive plastic and aluminum one (perhaps mistake number one) and always worked fine for the tired stock 3.9. The temperature with the new motor is fine most of the time, but since I even more recently had the AC revived (it had never worked since I bought the car) I found the engine gets quite warm when the AC is on and the car is under load. The other day I drove it out to go camping, fully loaded with gear and 3 people, and when climbing hills with the AC on, I could watch the temp needle start to move further and further to the right (up to about 3/4 on the gauge) with the outside temp at only about 72F. Come level ground, it would drop back to center. doing the same thing with the AC off resulted in no change of the temp needle. This concerns me, because should I want to go somewhere in the desert during the summer (90-100F) I fear I might roast it. My engine builder thinks that the aluminum radiator cant handle the extra heat from the condenser when the AC is on, and that I should try to find a stock copper/brass radiator to put back in. My goal is to be able to climb mountains in 100 degree heat with the AC on, which should be possible, is that the way to go? Is the factory copper/brass unit that good? Or should i try to find one of those crazy expensive welded all aluminum ones?