Spray carb cleaner at the gasket. If you hear a change in engine noise or engine speed, you have what is called a vacuum leak.
If it is leaking from a bad head gasket, it is because of a bad head gasket. If it is leaking from a bad intake manifold gasket, it is because of a bad intake manifold gasket.
The only fix for a bad intake gasket is to remove the intake manifold and replace the gasket.
What engine? and ensure it is a bad gasket, not an intake plentum.
Yes. Antifreeze is actually pumped through the intake manifold. If the gasket is bad it is possible that it leaks out
It could.
No. The intake only deals with air and fuel
Yes, a bad intake gasket can cause coolant to mix with engine oil. Indeed a bad lower intake can cause this. Who ever said the head gasket is a moron. You can't assume this all the time. This is why you have diagnostic tools such a a compression tester and a leak down tester. For example, my compression is good, and the valves are not leaking past the specs. However, there is air coming from the lower intake. The gasket is bad. Also, it's always suggested that you change the oil after the gasket just to be sure no water got in the oil pan from doing the gasket.
The Intake gasket is leaking, NOT THE HEAD GASKET. Replace the intake gasket
A pressure test on the cylinders will tell if you have a bad head gasket. If you hear a whistle sound near the intake gasket, spray WD-40 (or any type of petroleum spray) on the area and if there is a leak the engine rpms (or engine sound) should change.
a bad head gasket or intake manifold gasket.
It could. Check the coolant in the radiator and in the overflow container. If there is a film of oil on top after it has been sitting for a while, then you have a potential head gasket issue. Keep in mind that other things can cause the same symptoms, such as a cracked head, bad rings, or on a GM v6 or v8, an intake gasket, or even a leak.
It can allow water to mix with the engine oil and destroy the engine.