Hello. I'm new to the forum. Recently I bought a used 2001 C70 Coupe with about 137k miles on it. Barring random dings it is in very good condition.
I drove home from work today and it took and the radiator fan didn't stop for about 15 minutes. When it finally stopped, I attempted to crank it again so I could move it and I had absolutely no cranking power. It clicks when you try and crank it.
Is this a symptom of a bad thermostat? Battery perhaps?

 

Fully charge battery, clean all connectors to battery and starter, make sure all connectors have tight clamping to wires and connections. If in USA take to most auto parts stores and they will check charging and battery systems for free. Get vehicle codes read. Good luck! Thermostat cheap replace. Check radiator hose connections and after starting and up to temp the hoses stay firm.

 

The fan on these cars are known to run after you turn the car off sometimes. It's an intended feature. That being said, it sounds like it just drained your battery too much, hence the clicking when you try to start it now. I would take your battery to an auto parts store to have it charged and if necessary, replaced. I wouldn't worry about this happening that much though... I've had my battery for about 3 years now and it's fine even with the fan running after the car shuts off. The previous owner was probably aware that the battery was weak in your car before you bought it, is my guess.

 

Sounds like the battery is on its last legs... good advise on cleaning wires/connections etc. Also if you have a volt meter, you can do your own alternator test (look for Youtube vids). 1) Car off, measure battery voltage - should be 12.6 or so 2) start car, measure voltage at battery - should be 14V-14.5V or so 3) turn on every possible eletrical device, ie heater blower on high, radio, rear window defroster, high beams etc. Measure voltage - should still be 13.5V or more. Second thing is to note the position of the temp gauge if the car runs hot, I'd suggest you replace both the thermostat and the engine coolant temp sensor(s). Its the temp sensor that tells the fan when to turn off. An out of range temp sensor will keep the fan on longer than necessary. Also inspect the thermostat for deposits. If all clean then you can do a simple distilled water flush and refresh the coolant. If you see rust etc you may want to use a mild commercial flush.

 

real good advice here from some good members!