[masraum]

Originally Posted by A930Rocket

What’s the best place to measure water temperature on an engine? I placed my sending unit on the radiator hose where water exits the engine.

I would think this is the hottest place to measure, unless you find somewhere at the back of the engine with less airflow. Would it be beneficial to know the radiator outlet temperature?

That said, I was seeing 210° On my autometer temp gauge driving at about 60 miles an hour. When I slowed down to 45 or 50, it cooled down to 195°. I don’t know if this was the thermostat opening and closing or what?

I think on the engine would be a better place to put the temp sender, but I think it's also certain places on the engine, not just anywhere. I assume you'd need a computer model of the engine coolant to know for sure. Where is the factory gauge sender?

Edit: The aftermarket temperature gauge is making me paranoid, because the instrument cluster gauge is pointed straight up and down. On an E46, this means it’s in the normal range.

I think you'll find that most factory gauges that do NOT have numbers are not really linear gauges. I think most factory gauges today have 3 basic readings, low, regular, and high. I think you'd find that 160-220º (or something like that) all put the reading in the "normal range." I suspect you wouldn't notice a difference until the temp hit 250-270º (boiling point of coolant at 16psi). I think many/most manufacturers heavily dampened or rewired most of the coolant temp and oil press gauges years ago to eliminate issues due to people not understanding what they are seeing.
I wouldn't think that 210º would be a problem

Edit 2: I realized today, my electric fan is not coming on. There is 12 V at the fan electrical connection. I hot wired the motor on the back of the fan and it spun up. The circuit board on the fan which is controlled by the DME probably toast. New fan and radiator going in next weekend. Hopefully, that fixes everything.

Yep, dead fan is certainly not a good thing.