Porous radiator?

Clouds of steam from the bonnet yesterday. Pulled over, think the expansion cap has let go. Topped up, limped home. Let her cool down. topped up, drove to get temp up, then parked up and left idling. I think, but I'm not certain, that there is steam coming from the radiator itself, but it may just be residual water evaporating off after it boiled over. Expansion tank doesn't seem to warm up (even though it has coolant in it), and nor does the hose going to the "single spout" side of the prrt.



Fans cut in normally.



Any thoughts? Is it possible/normal for a rad to fail like that? I had been topping her up occasionally over the last month or two.



HG replaced last August.

from the last news http://ift.tt/1AARmXM

via IFTTT