Sounds like a blown head gasket. Have a mechanic do a compression test, and check for oil in the coolant and/or coolant in the oil, (white foamy material around top of fluid level.)
A blown head gasket can allow coolant to see into the manifold, and out the exhaust. A broken piston ring can also cause this problem.
A manifold leak is usually in reference to a failure of the intake manifold gasket. It can leak air, oil or coolant. It can leak to the outside of the engine or internally into the engine. A manifold leak may also refer to the Exhaust manifold that is leaking exhaust fumes from a bad gasket or a crack in the manifold.
It could just be condensation which forms in the exhaust system outside of the engine, or you could be leaking coolant into your engine (typically via the head or intake manifold gasket).
The heater core is leaking coolant.
leaking gasket try tightening the bolts a little might help
If the exhaust manifold gasket is leaking the only fix is to replace it with a new one.
No.
Valve cover gasket
Most of the time - yes
manifold or downpipe gaskets may be leaking gases or worse, cracked manifold
Intake manifold is leaking, or worse, cracked cylinder most likely tho, the intake manifold.
you need to replace the intake manifold gasket.