Overheating, or is my head gasket on straight?

[MX5Bob]

So, here's the deal. 1993, V-6, A/T (boo). Past few days it's been running cooler than normal in the morning, ambient temps in the mid-60s, about 10 miles of stop and go traffic followed by 14 miles of full-speed freeway and two miles of moderate speed surface streets. Temp needle barely budges above the bottom.

Afternoon, ambient temps in the mid-80s to low 90s, trip is reverse of the morning with more stop and go last 10 miles. Temp gauge about half-way up most of the way until the stop and go. It's been reading really close to the red. Until today when it overheated.

Radiator is full. Thermostat, radiator cap, main hoses all new.

Head gasket? Clogged radiator?

[sonofa]

Fan clutch.

[MX5Bob]

Originally Posted by sonofa

Fan clutch.

Sorry, should have mentioned, electric fan.

Turns out I have some kind of mystery coolant leak, the kind that doesn't leave any easily seen evident.

[sonofa]

Originally Posted by MX5Bob

Sorry, should have mentioned, electric fan.

Turns out I have some kind of mystery coolant leak, the kind that doesn't leave any easily seen evident.

I guess the coolant wasn't really full then....
Check your oil for coolant, check compression for possible head gasket leaks.
And put a proper fan back on it. If the electric fan isn't flowing enough air or doesn't come on when its supposed to, you could be losing coolant from excess heat rather than overheating from insufficient coolant.

Belt drive fans are much more efficient than electric due to fewer energy conversions.