E46 Clubsport: Loss of coolant... split radiator!

The Clubsport is starting to become a bit 'whatever next' lately. Amidst the other post new year jobs I forgot to mention the coolant expansion-tank that sits next to the radiator had swelled and split down one side, so a new one was duly fitted.

Last week the sudden loss of coolant returned, with the puddle in the same place under the radiator, but no visible sign of a leak. Nath assumed it to be the radiator-cap, so we pressure tested it in work and it's fine. Then we pressurised the rest of the cooling system and this is what we found - the radiator has burst along the top. A new radiator is going straight in, but the fact remains that something is still pressurising the cooling system and needs to get sorted.