Either. It all depends on the severity of the head gasket leak.
There must be a gas leak. Contact your gas supplier IMMEDIATELY, if the smell is in a house. If it is in a car, have your mechanic check for a leak.
There are several reasons why a car would start and then shut off immediately. It could be battery cables, a fuel problem, or even a bad spark plug.
Depends on the type of car. My mom's car take about 5 minutes while my dads turns off immediately.
A 1994 Honda Accord can shut off for a number of reasons. The most common are lack of fuel or air. If there is a vacuum leak the car will idle erratically and shut off. When a car runs to lean it may not be able to hold an idle.
exhaust leak or a possible fuel line leak
There are innumerable points for the leak, cost for repair will depend on where it is. You can drive the car only if the leak is minor and the temperature gauge shows normal temperature.
if it is under the hood, it could be a small antifreeze or oil leak that when the engine is running the smoke is blown away, but when shut off it continues to burn off but is not blown away.
Like with Duck tape?This is not illegal unless:You are going to drive the car and this is the only way it is held shut.
If it it shutting off because of the hissing, it is likely moisture getting at electronic parts and shorting them. The hissing would be caused by cold water contacting hot engine parts. If the hissing is only heard after YOU shut off the car, it is likely a small leak in a vacuum hose. These are usually easily fixed.
you may have a head gasket leak. And check under your car for fluid leaks. A head gasket leak is serious get it check out immediately.
oil in antifreeze is a sign of a head gasket leak, shut car down before major damage is done.