My VS commodore is overheating. I have a small leak from my radiator that I noticed a couple of weeks ago. Since then, I have been regularly topping up my coolant/water to make sure I don't run dry, just until I can get to a radiator specialist. In the process, I have diluted the recommended 50:50 mix to about 30:70 coolant/water. Strangely, the heater/fan in the interior is reflecting the movements in my temperature gauge, which is moving up and down quite quickly. When the gauge lowers towards 'Cool', heat comes out, when the gauge moves up towards 'Hot', I get cool air. I replaced my water pump about a year ago, so it is not that. I thought maybe my thermostat was buggered, but the coolant/water is genuinely heating up, so I think the thermostat is fine. The radiator cap does not get hot, but when I open it, coolant comes gushing out. Due to the fluctuations in the temperature gauge, the heater playing up, and the radiator cap not getting hot, I am thinking that I have a partial blockage in my radiator. Please help!!