Reply #19: Coolant reservoir is meaningless [View All]

The only measure of the radiator level is what's in the radiator. When the engine's cold, pop the top on it and take a look.

As others have suggested, if it's full you can suspect the thermostat or the fan. If the fan doesn't turn on after a few minutes of idling in warm weather, bingo.

The water pumps in Toyotas are pretty solid and unless you're at some multiple of 75k miles or so it's unlikely to have gone tits up. Thermostates are pretty easy to change out. It's also possible that the radiator has simply corroded too much internally and won't flow enough fluid. If you pull it, you can easily check for this since it'll crumble when you run your fingers over it (this happened to my old 90 Camry once).

The green antifreeze is corrosive - the orange stuff sold by Mercedes is more expensive and much gentler on the cooling system. You can also get your engine oil analyzed for radiator coolant to see if you have a head gasket leak.