Dear robertmfranklin,

Hope you're well. Is the ignition power stage - a flat device, with a gray top, mounted in the inner fender well, behind a headlight - the factory-original item? If so, it could be "on the way out". With 200K miles, it doesn't owe you a penny. On turbo-equipped cars, the ignition power stage may be heind the passenger-side headlight (on non-turbo cars, the ignition power stage is behind the driver's side headlight).

When ignition power stages fail, they work "intermittently". Exposure to heat usually produces signs of failure, e.g., the car won't re-start when "hot". In your car's case, higher ambient temps in winter may be enough to cause failure.

Another source of failure is the crank position sensor. This sensor - mounted in the transmission bell housing, on the passenger side of the engine - usually shows signs of failure in wet weather. Water gets at the wires, through a crack or cracks in the sensor's wiring harness insulaton sheath. Water on the sensor's wires causes the sensor's signal to be lost. Without the sensor's signal, the engine control unit shuts down the fuel pump.

I'd be wary of cooling system sealers. They could clog waterways in the radiator, and so make the radiator less efficient. That makes the engine more likely to overheat.

A mechanic can do a test to see if exhaust gases are present in the coolant tank (i.e., if the headgasket has failed). If exhaust gases are present in the coolant, then the headgasket has failed. If not, the coolant loss occurs somewhere else. I recall posts reporting coolant leaks where the coolant landed on the engine, and burned-off. As a result, there were never any signs of coolant on the ground.

When was the radiator last changed? In the US northeast, a radiator might last 12 years. Anything beyond that, and you're on borrowed time. When were the radiator hoses last changed?

Hope this helps.

Yours faithfully,

Spook