VS overheating

[Darcy78]

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. Sometimes, 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 or seized thermostat. Please help!!

[IBLOWN]

Sounds to me like the thermostat. The temperature sender is in the thermostat housing. If the thermostat is closed the water in that area will be hot, then it opens and it cools.

Having the heater on cools the water in the heater core as its not circulating because the thermostat is closed.

[Darcy78]

Thanks IBLOWN, that makes sense. I am a bit of a novice when it comes to cars!! Appreciate the reply.

[hako]

The coolant that flows to the heater by-passes the thermostat - this is so you can use the heater before the thermostat opens otherwise it would be cold for miles and miles.
From the sound of it, you have air in the system caused by the coolant leak from the radiator. The air trapped in the system can prevent coolant from flowing thru the heater.
Radiators can be bought new with warranty for about $100 so that would be my first fix.