water system/coolant question

[beneldude]

Hello,
This is possibly a daft question!
I'm trying to flush out my pipes!! As I think there was a blockage, perhaps an air block or gunge block. I removed the rubber pipes that lead to the radiator and stuck a hose into the pipes that run right to the back. When I put it in one pipe the water overflows out of the coolant tank at the back. When i put it in the other pipe it just comes back out without causing an overflow in the coolant tank....is this correct?

Cheers

Ben

[Mocki]