You do not need to add a sealant to the gasket. Just make sure you torque the bolts to factory specs.
Do not use sealant on the head gasket. I use permatex on the threads of the bolts that go into water jackets.
I was looking at fordparts.com and it shows a water pump gasket
Your cylinder head gasket needs replacing.
The head gasket is gone and water or coolant has mixed with the engine oil. Replacing the head gasket is no big deal.
If you did not get the water in your oil from replacing the gasket then you may have a coolant passage leaking into an oil passage. Another answer may be a gasket that is not exactly like the old one. Sometimes the parts store issue a wrong part or may be from a bad aftermarket gasket.
The housing retainer bolts are loose or the gasket has deteriorated. If replacing the gasket, use pliable gasket sealant to improve the seal. it could also be the water pump went bad and leaking water down beside the thermostat. the thermostat is part of the water
a blown head gasket needs to be replaced as early as possable. it will only get worse and additives like water glass, etc will gradually worsen the problem.
Bad installation. Try some permatex "gasket maker" and re-do it. dave
WATER. This indicates a blown head gasket. Damage has been done to the engine in the form of overheating and the head gasket(s) have blown. Water therefor has leaked into the oil. Replacing the head gaskets is the way to repair this motor.
Sounds to me like a cracked head and or a blown head gasket, i had a similar problem but it was on a Saturn
Did you remove the head?.....If so, the head gasket is probably incorrect or incorrectly installed, or possibly a cracked head or block.....Why did the freeze plug need replacing?....
I'VE BEEN TOLD A SHORTCUT TO REPLACING THE WATER PUMP IS TO REMOVE THE EXHAUST MANIFOLD AND THE WATER PUMP WILL COME OUT EASILY. THEN OF COURSE, YOU HAVE THE EXPENSE OF REPLACING THE EXHAUST MANIFOLD GASKET AND EXHAUST O-RING GASKET. BUT A LOT CHEAPER THAN REMOVING THE WHOLE FRONT OF THE MOTOR. Try a chiltons manual or www.alldata.com If this is a quad four motor, you may not want to try this at home.