another nc30 overheating

[Deviant400]

as above, the rad cap is not 100% sealing the system

[speedy231278]

But why would my coolant still boil?

For the reasons other people have already stated. Either there is air in the system, there is a leak, or the bike is very severely overheating. The trouble with leaks is that even a very small one can cause enough pressure loss to overheat the bike but without being visible. This is because the coolant either evaporates as it leaves the system, or gets burned off by the heat of whatever it falls on (or just pisses out and never lands on the bike). When you switch off, the system loses pressure, and you get a vacuum holding it in unless the leak is severe. One thing you can do is pressure test the system if you can find the right kit. Basically with the system full, you attach a bit of kit to the radiator filler and use it to pressurise the system to full running pressure. If there's a leak, pressure will be lost over time, and you will hopefully find where it is coming out.

If, as you say, the pump and stat are fine, it surely has to be air getting into the system. Other than that, the only other thing I can think of that would cause boiling would be head gasket failure, and that's a fairly rare thing on our little V4s.

[ohcheese]

It'll probaly be the cap than.

It's a new one, but when I crashed my top radiator got a little smack. Maybe the neck isn't perfectly round anymore? Should check that out tomorrow.

If that is the case, could I bend it back? Or best get a replacement? (I'm a student so although I do my best to maintain her properly I try to do things on budget)

[tigerclaw]

You might be lucky and be able to bend it yourself, but more likely take it to a radiator (or similar) place and see if they can heat it and bend it right. But its a long shot, personally when it comes to overheating rather spend the money and get a sorted (new or second hand) unit, if the bike does overheat properly then it will cost you a lot more money (skimming of heads etc etc). I would suggest you get a radiator place to pressure test your system first and to check the radiator cap and where it seats so that you know 100% thats its not something else (ie you dont spend money in the wrong direction), they should check it for free, its simple with the right tools