Weird hissing after ignition off, possible vacuum leak? (1 Viewer)

[bigred1]

Greetings,
I noticed this last night and seem to remember hearing it before and forgot about it.

I turn on the ignition, but dont start the engine, then turn off the ignition. After about 10 seconds I hear a weird hissing sound coming from behind the air filter housing, assuming its from the vacuum system. Its seems to "off gas" and quits after maybe another 5-10 seconds.

So does the vacuum system pressurize without even starting the engine? Could this be a leak or is it something like a depressurization thing going on?

Thanks for any input on this....
Dustin

 

[2mbb]

vacuum is only created when the engine is running. However, the brake booster acts like a vacuum tank and should hold vacuum for some time after the engine is turned off. However, I wouldn't expect the key to have any effect on the brake booster--but stepping on the brake pedal will.

If you're sure all you're doing is turing the key, then I would suspect the fuel EVAP system. There is a key operated solenoid. Next time, before turning the key on, take of the gas cap and see if your gas tank is pressurized.

 

[bigred1]

Thats got to be it. I didnt press the brake or turn over the engine. Makes perfect sense, thanks.