Draining coolant

Possibly a silly question, but is there a foolproof method to drain all the coolant out of the system without having to take drastic measures? I've just had to replace the heater matrix hose set after the connection to the cylinder head went bad and kept splitting. Despite the system having been topped up to get us home, I only managed to get about 2 1/2 litres out after disconnecting the bottom radiator hose. This mirrors what I found the first time I worked on the coolant system. The previous time, I always found that 2 1/2 came out, and 2 1/2 went back in. Only after removing the thermostat housing to replace the stat did I ever get the full 4 1/2 back into the car.



Does the stat trap coolant in the engine unless it is either in the open position or removed? I seem to recall discussion about drilling a hole in the flange on the thermostat to aid bleeding, but I don't know if a lack of one would cause a lock. When I added clean water to flush the system, it came back out pink, indicating it had mixed with coolant still remaining in the system. Even after having the heater hoses off, nothing more came out. Yes, I did have the expansion bottle cap off, and also the bleed screws out. Then I wondered if I left the bleed screws in whether or not this might allow the remainder so syphon out when I drop it again to removed the cleaner and flush it again?



I did see somewhere a suggestion to crank the engine over a few times to pump it out, but I don't really like the sound of that!

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