Chevy Spark with over 100,000 miles. Fluid in overflow tank looks a chocolate milkshake. Chevy dealer says trans cooler leaked allowing coolant into transmission. I'll get a low mileage transmission for $300 and a new radiator for $100. What's the best way to clean out the transmission fluid from the cooling system? I was thinking, take out the radiator from the circuit as well as remove the thermostat temporarily and somehow connect the two radiator hoses together. Add some water based solvent and run the engine a few minutes. Drain and repeat. Do they make a specific solvent for this purpose? Any other ideas?