Radiator hoses collapsing?

[John_R]

I recently got a 93' 240sx Vert. I've been fixing a lot of the little problems (Tie Rod Ends, Belts, body panel alignment, etc. ).

Anyways, when I got the car it had flattened radiator hoses. So I pulled some off an S13 Parts car that were in good shape. drained the fluids, installed them, drove it a bit. Checked everything. Temp was down, fluids weren't leaking, everything seemed great. Took it on a small trip and opened the hood and found they had collapsed again.

What could cause this? I would assume that one side of the pump is blocked or something? Whatever it is, whats the first step to diagnosing this problem? (not to mention, there is a new water pump and new hoses, where to go from here?)

Thanks a lot guys!
John