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Hissing with key in the on position but engine off.

Help, Advice, Owners' Discussion and DIY Tutorials on S40 and V40. In this forum you'll find S40/V40-specific owners asking and answering questions on maintenance, ownership, repairs, tutorials and almost every do-it-yourself thing you can do to save money owning these Volvos.

1996 - 2004 S40
1996 - 2004 V40

Sf3500
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Sf3500

Hissing with key in the on position but engine off.

Post by Sf3500 » Sat Aug 03, 2019 2:54 am

Just recently, I have noticed the car begins to hiss and release a gas of some sort into the cabin, I say it's a gas because it is often accompanied by harsh cough and watery eyes.

What could this hiss possibly be. The gas is odorless and colorless. Here is a video of the hissing noise. Can somebody please help me identify where the hissing is coming from. Keep in mind the climate control system is set to off in the video.

Edit: mine is a Volvo s40 2004 1.9t



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abscate
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Re: Hissing with key in the on position but engine off.

Post by abscate » Sun Aug 04, 2019 3:29 am

Probably either normal AC hiss from rundown, or, if gas is released, a hole in the evaporator. Your AC will stop working pretty soon if the evap gets holed.


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alschnertz
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Re: Hissing with key in the on position but engine off.

Post by alschnertz » Mon Aug 05, 2019 2:26 pm

My '01 makes noises under the dash on occasion. Definitely coming from the heater blower motor area and does it when stepping on the brake. I don't believe the sound is vacuum related as it will make the radio static(y) at the same time. I suspect it's a wonky ECC in my case.

I can't think of any toxic gasses other than R134A which will dissipate rather quickly, like within minutes, as it empties your A/C system.
The only other thing would be coolant from a leaking heater core which may be somewhat irritating.


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abscate
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Re: Hissing with key in the on position but engine off.

Post by abscate » Wed Aug 14, 2019 6:59 am

The late P80 and P2 HVAC systems have an after-run feature will which leave the blower on low speed - if you have some oil reside in the motor it might t be picking that up and pumping it into the cabin when the engine is off and the car still.

Refrigerant doesn't really sting your eyes - its an inert gas. Also an AC leak ends in seconds or minutes at most.


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