sounds like intake gasket did mine last year be sure to use little lock tight and torque to older 70s spec had no problems yet
There are several possible causes, only a pressure test of the system will tell. The GM V6 had some issues with intake manifold sealing, and there have been at least 3 different gasket designs that I am aware of.
Perhaps you didn't plug the connection back in. It would be the single wire connection that runs over the valve cover on the drivers side.
Your water pump is bad
The 1998 most likely has a Northstar engine. On this engine the starter is under the intake, and the intake has to come off for replacement.
Intake Air Temperature (IAT) sensor 1 circuit high input. Check the connection at the IAT sensor.
What are the intake manifold torque specs for a 1998 ford f-150 xlt
In a 1998 Mercury Villager, the mass air flow sensor is located in the air intake tube. The air intake tube goes from the air box to the intake.
Probably either the sending unit or a loose connection.
What engine? and ensure it is a bad gasket, not an intake plentum.
The intake valve is bigger.
IT IS LOCATED IN THE REAR OF THE INTAKE... YOU HAVE TO REMOVE THE INTAKE TO CHANGE IT....
it would be on the top of the moter