97 Grand Marquis: overheating and P0401
I have had an intermittent overheating problem. While driving, only happening about once a week, the temp goes up to redline, hangs for a few seconds (2-20sec) and drops to normal, them everything is fine for several days. Now it is doing it every day. two new thermostats and nothing, probably worse. Now, there is no coolant in the upper and lower hoses, and at operating temp, they are HARD. Cap is hissing. The overflow is full. it is like it is not cycling the coolant, even thou it has new water pump. I am also getting a P0401 code, which is EGR flow insufficient. Does that mean that I have a crack or bad head gasket and exhaust is entering coolant and building pressure in cooling system? HELP!