When my 86 300E idles for 10 minutes, it starts spewing coolant from the overflow tank. Driving around, this doesn't happen. The hose that goes to the thermostat is rock hard and the hose going to the overflow tank is squishy and limp. I replaced the thermostat last week thinking that was the problem, but obviously that was wrong. Could something be plugged and why only when I am idleing in park? And you don't need to say "don't idle your car dumbass".

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