Unburnt gas leak is probably referring to natural gas. The gas is mostly methane which is odorless, that's why they add that additional 'rotten-egg' smell to make it noticable. That smell isn't a health concern, though the gas is a hydrocarbon and probably has some health risks if exposed to it for a long period of time.
Because the acid can leak out and cause damage to the equipment and to humans.
Any coolant leak can cause an overheat.Any coolant leak can cause an overheat.
can exhaust manifold leak cause you to burn oil
There are several things that can cause your fuel tank to leak. The most common cause is a hole in the fuel tank. A loose fuel line can cause the fuel tank to leak.
Find the leak, and fix the cause.
you have to find where the leak is first.
Find leak, repair/replace cause.
engine oil leak
no
a small evap leak would not cause your car to jerk.
Yes, that can cause the fluid to foam up and leak out of the vent.
I would not expect a valve cover leak to cause a car to stall. A valve cover leak can fill the spark plug area with oil which can cause rough running.