I noticed steam coming from under the hood of my 1996 Mercury Grand Marquis. I added very little anti-freeze & replaced the thermostat. I keep noticing the coolant filler jug being low after each drive, but have no overheating. I add about 1 quart water each time. Do you think it’s a crack in the intake manifold? Is it easy for me to replace? If not, how much will it cost (ball park) to get it fixed, parts & labor?