sound of pressure being released...

i've noticed when i come to a complete stop, my car sounds like it is releasing a burst of pressure (like a blow off valve on a turbo car), but no turbo under my hood. just wondering what it could be...

its a 328i

Where's the sound coming from?

Check your coolant level....

coolant level was a little bit low, but hardly added any could it possibly be a leak? but how does that explain the pressure sound? and yes it sounds like it coming from the engine bay.

CCV would be my first guess.

i dont think it is because my car is never low on oil....

What's the history of your CVV? Replaced ever?
Mileage on car? Short trip car?

Do you have an after market intake?.

no, it is stock

idk if the CCV has ever been replaced; the car has 228k miles and i do majority of shorter trips in the fall and winter because i am a student that drives to campus 4 miles round trip.

Originally Posted by three28iguy

no, it is stock

Originally Posted by three28iguy

idk if the CCV has ever been replaced; the car has 228k miles and i do majority of shorter trips in the fall and winter because i am a student that drives to campus 4 miles round trip.

good god if it's the original CCV that needs to be changed immediately among other things lol.

hahaha i bought the car with 119k so i really have no idea what has/has not been replaced, i just assume nothing has ever been replaced... the only time i can fix things is in may, but for the time being i am just figuring out what exactly i have to replace. i am going to do a coolant sysdtem overhaul and CCV in may.

Does that sound occur somewhere in the 0-10mph range also?

yes it does sometimes when i first begin to accelerate...

Originally Posted by R. Cate

Does that sound occur somewhere in the 0-10mph range also?

Mine has been doing this since I bought the car... I never gave it much thought because I dont hear it most of the time when the radio is on. Do you know what causes it?

yeah mine definitely makes the pressure being released noise when accelerating from 0-10mph today i listened for it to make sure

Originally Posted by three28iguy

yeah mine definitely makes the pressure being released noise when accelerating from 0-10mph today i listened for it to make sure

This would be easy if your car was turbo or supercharged because that sound 99% of the time is a boost leak! lol. So maybe you have a vacuum leak? do you have loss of power?

no loss of power the motor sounds great and runs smooth, it sounds like an atmospheric bov, but not nearly as loud

i had that exact same thing on 2-year previously owned E46 325ci since day of purchase, left it as is

Originally Posted by heztheone

i had that exact same thing on 2-year previously owned E46 325ci since day of purchase, left it as is

hahaha yeah, i guess if i dont figure out what it is i'll just do the same, but it's still weird and doesn't make any sense...maybe over the spring when i replace my CCV i'll figure out a logical explanation for it, until then thanks for everyone's help. cheers.

Might be a leaking check valve on the brake vacuum booster. If you shut down the car and wait until the hiss goes away, do you still have brake assist?

i was reading on E46fanatics that the "Hisssssshhhhh" sound is a sign warn bearings in your water pump.

I changed my waterpump after i got my car, and it has still made the hiss for the last 30K miles

With the car parked, try doing a "bounce test" on the front fenders on both sides. A hissing sound, like releasing pressure, over small bumps or abrupt stops, was a warning that my front left strut was blown.

its not the struts; it only hissees when i accelerate from 0-10mph or come to a complete stop