My commodore has recently started overheating. I can't see any leaks in the engine bay or underneath. It seems to blow out through the overflow. A 20 minute driver will see the gauge go up to half. Any longer and it goes up and beyond the next mark. When I check the radiator its down quite a bit. I did a pressure test on the system. It looked OK. Didn't drop. Just after some ideas as to what is going wrong. Cheers.
Could be a blown head gasket that is pressurizing the cooling system, take it to a radiator guy and get him to check for gases, they put a device on the radiator that will tell whether it's blown or not.
V6 Ecotech or V8 LS1? Had a problem with a mechanical component of the thermostat getting 'stuck' on my Ecotech that would cause it to overheat (or read as overheating). Got it replaced and all was well again. Also had it happen on a couple of mates Ecotechs over the years.
I would check that the thermostat is opening properly and that the thermo fans are working Actually it wouldn't hurt to replace the thermostat & gasket anyway if you don't know when it was done last It has been ridiculously hot & humid in Darwin of late and I have noticed that my Tonners temp gauge is even reading a little higher than normal
