Legacy cooling problem

[b3lha]

I know this is an SVX forum not a Legacy forum, but I reckon somebody here will know the answer to my problem.

My '96 2.2 Legacy has an overheating problem. The water in the engine is boiling but the water in the radiator remains cold.

My first thought was the thermostat might be stuck closed, so I cut the centre out of it with a hacksaw. Then water started pouring out of the weep hole on the water pump - meaning that the ceramic seal had failed. So I've just fitted a new water pump and thermostat - but the overheating problem remains.

Once the engine warms up, the top corner of the radiator (near the inlet pipe) is hot but the rest of it is cold. I wondered if the radiator might be clogged, but if I squeeze either hose, I can make water overflow from the filler cap - so there's definitely a pathway through it.

I reckon the heat is spreading to the radiator via convection rather than the water being circulated by the pump (ie. stat closed or other blockage). I keep thinking that maybe there's no water in the water pump, hence why the stat isn't opening and why the seal failed.

My plan is to try the gutted thermostat again as this will at least ensure that I don't burn out the seal in the new pump. And while I have it apart, I'll pour some water into the top hose and see if it find's it's way though the block down to the pump.

I don't understand how the engine is supposed to fill up with water. Obviously it has to fill through the bottom hose, but if the stat is closed then it can't - and if there's no water in the engine then the stat won't open. Catch 22 AFAICT.

Anybody got any ideas?