I have the same problem. so far I've replaced the thermostat, heat coil and I'm in the process of replacing the waterpump today. My suggestion is to sell the car. Cougars are worthless, don't get stuck dumping money into it like I have. I owned mine for a month before it went to shit. since then it's been one repair after the next. It hasn't run right 8 out of the 9 months I've owned it. This'll be the last mercury I ever own. Btw the engine isn't getting water through it is your problem. Try what I tried but start with the water pump.