Thanks for your reply Lateralaus, this problem is driving us nuts atm 1, All parts are genuine and correct. 2, The motor spits the water out via the overflow bottle rather than circulate it hence it overheats 3, If remove the thermostat and bypass the overflow bottle the temp gauge starts at cold then runs around half in city traffic but cools on the freeway . 4, there are no leaks anywhere. This motor just seems to be doing everything it shouldn't cooling wise other than that its a gem , just like all the motors this guy has previously built for me ,We have to laugh or else we would go nuts lol. The reason for the rebulid was at 320,000 k I bent the crank :( So we completely stipped it down cleaned everything got a new crank , new gaskets etc it started first turn of the key but the temp wasn't right from the word go:( The friend who has done the rebuild is a top spanner guy and the other motors he has done for me have had other 200,000 k put on them before I've sold the vehicles ( I do about a 1,000k a week lol) And this V6 was returning about 700k per tank .anyways will keep you posted we are thinking of taking the heads off again in case it was a faulty gasket , thank goodness its only costing me parts . Cheers Lozza