Had a few issues with my cooling system on my Blazer recently, but it's only just now that I'm starting to have issues with it running a bit hot.

I replaced the radiator as one of the tanks had cracked. Shortly after that the seals on my water pump failed and it lost a lot of coolant. I replaced it with a new Gates pump (most readily available in the UK). At the same time I flushed the block and heater core.

It then started running rather hot, around 230F. And the temperature would continue to climb. I found that I had an airlock in the system. Later I replaced the thermostat, as it was still running hot.

I filled the coolant system to the bottom of the stat opening before refitting the stat and housing to reduce the possibility of an airlock in the block.

I'm pretty certain there's no air in the system any more, but it still runs 210-230F.

Any ideas?

 

Is the fan clutch working OK? It should not spin freely at any temperature. It should have some resistance to turn it by hand when cold, and when the engine starts to overheat. It should "roar" when cold on acceleration, then quiet down after driving. Depending on how cold the clutch is when you start the engine, it should quiet down around 2500 engine rpm and above.