[Christ]

Originally Posted by Daox

Unfortunately, radiator size has nothing to do with warm up time. You must reduce the volume of coolant within the engine block to warm up faster.

This is only half true.

The thermostat doesn't stay closed. When the temperature of the coolant near the thermostat reaches the limit of the thermostat, it opens until coolant which is not at the limit temp touches it and cools down the wax inside. This happens usually at least once before the temperature gauge even moves.

It will happen a handful of times before the engine is "warmed up", and even more before you get to the point where the engine is /thoroughly/ warmed or temperature stable.

Every time the thermostat opens, it lets the hot coolant into the radiator. A larger radiator will allow the coolant to spread over more area, thus cooling it faster. So yes, indirectly, a larger radiator will affect warm-up times.