UK Car Repair: engine overheating, renault laguna 2, outlet pipes

Question
Hi, I have just replaced radiator on Renault Laguna 2.2 turbo diesel.Old radiator was leaking, but if i kept topping up the water, the car ran perfectly well.Now,with the new radiator, the engine is overheating. I replaced the thermostat in case it was not opening and this has made no difference. The oil is fine and the cooling system doesnt appear to be leaking.Ive bled the system and topped it up over and over but still no luck. Any likely causes, any advice greatly appreciated!!

Answer
From what you say, one would conclude that the problem is the new radiator.  Were there any plugs/paper/etc in the inlet/outlet pipes?  Otherwise to check the flow you would have to drain it, disconnect the hoses then run water through it with a garden hose.