Coolant vs Metal Temperature

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I recently saw on a forum someone asking how it can be possible to see a higher coolant temperature at the same time as our coolant is keeping the engine cooler. It's not as crazy as it sounds!

First, let's not confuse coolant temperature with metal temperature. People tend to focus on coolant temperature for two very good reasons, it's visible on the gauge and engine overheating starts with overheating the coolant. If you're on the edge of overheating your coolant (220-230F), another 10 degrees will push it over the edge. The metal components, however, don't care about a 10 degree rise.

The metal components can become overheated once antifreeze boils to vapor inside the engine. Local boiling around the exhaust valves will empty the cooling jacket there of liquid antifreeze allowing the metal temperature to spike by hundreds of degrees.

The temperature of our coolant can be higher at the gauge (we're talking 10 degrees or less - not much) while keeping the metal temperatures at all locations under control. See? The science does make sense once you understand what's going on internally!