My beautiful coupe sits for 6 months every year. This year all was great on start-up. Drove about a mile to say hello to my mechanic. When returned to car there was a quart+ or so of coolant on the ground. Put it on the rack and no sign of broken hoses, etc. and no leak. Drove into town (10 miles) and back home and all seemed OK. When I went to add more coolant the next morning, it had again dumped another load. No sign of any leaking when refilled and started up, but not driven for any distance. Since I'm not under the car when it takes a dump, I can't verify where it's coming from - again no sign of broken hoses, etc. It does appear to be coming from near the reservoir which isn't cracked or broken and there isn't any trail or pooling of coolant. Cap appears to be good. Doesn't overheat (but I'm sure it will if/when it drops enough coolant) and runs normal temp so not a stuck thermostat problem.

Any help/ideas much appreciated.

 

Normal temp on the idiot temp gauge?

It doesn't move off center until 230 degrees.

Thermostat would be the first thing I would think of.

 

+1 on sticking Thermostat

If not, then next check the Water Pump.

Graham

 

Besides the lying temperature gauge, if it dumps a sufficient quantity of coolant, the level can fall below the temperature sensor and you will never get an overheating indication at all, and end up with major damage from a fried engine.

Do not drive this car until it is repaired.

+1 on thermostat being the most likely cause. The system should also be pressure tested for leaks.