What would make your car do a hissing sound then after a few minutes stops?

Question

Doesn't do it all then time..just every once in awhile then it quits and may not do it again for weeks.

Answer 1

Could be a leak in a hose, like the radiator hose or a different one.

Or could be brakes.   Take it to a small local mechanic shop.

Answer 2

It sound like a vacumn hose leaks.   There might be a small hole or crack in a line and only make noise when the hose moves.  If possible have someone listen under the hood when it happens to try to find the problem.

Answer 3

Maybe it's the air conditioner, see if it happens when you use the A/C.

The A/C system works because of pressure differential. It's usually the pressure equalizing in the A/C system that creates a hissing sound just after you shut down the engine. This is normal.

The gas in the system is pressurized to a liquid by the compressor. Then the liquid is pumped to the condenser (a heat exchanger in front of the radiator) where the heat is removed from the liquid. The liquid then passes through an orfice (like a garden hose nozzle). On the liquid side of the orfice is high pressure. when it passes through the orfice the pressure drops, the liquid expands to a gas and absorbs the heat from inside the car through the evaporator (a heat exchanger inside the car). The gas is then sucked back to the compressor and the cycle continues.

If you are not losing engine coolant or having any other problems this is most likely the noise.