hissing from under dash/firewall area

drumsbeloud · Mar 23, 2006

I've just noticed a hissing noise coming from somewhere under the dash or possibly in the engine compartment up by the firewall. It seems to be coming from near the middle of the car. I assume it's an air leak, so any suggestions what might be leaking? I checked all the easily accessible vacuum hoses and my boost gauge is reading in the normal range. I *thought* I smelled a slight wiff of coolant when I got into the car this morning...but I could just be paranoid.

Any help would be appreciated.

uiuc240 · Mar 23, 2006

Boost leak? Might not show up on the gauge at first, as the turbo will simply blow more air to compensate. When it gets really bad, you'll know...

pasadena_commut · Mar 23, 2006

drumsbeloud said:
I've just noticed a hissing noise coming from somewhere under the dash or possibly in the engine compartment up by the firewall.

You really want to be sure that it isn't a coolant leak.

Leave the car running, open the hood (carefully, if you have a coolant leak you don't want to get sprayed) and listen around in the engine compartment. Look under the car for drips. When a pinhole leak first starts it may not leak very much.

Then let the car cool down completely, take off the radiator cap and check the level there. If it's leaking coolant the level in the overflow container may look normal even when the radiator is half empty. At least that's the way it was on my old 323 when it had a pinhole leak in a cooling pipe. That car made noise under the dashboard of the "gurgling" variety from the air that got in where coolant should have been.

drumsbeloud · Mar 23, 2006

uiuc240 said:
Boost leak? Might not show up on the gauge at first, as the turbo will simply blow more air to compensate. When it gets really bad, you'll know...

i don't think so, as i checked all the vital hoses, gaskets, etc.

drumsbeloud · Mar 23, 2006

pasadena_commut said:
You really want to be sure that it isn't a coolant leak.

Leave the car running, open the hood (carefully, if you have a coolant leak you don't want to get sprayed) and listen around in the engine compartment. Look under the car for drips. When a pinhole leak first starts it may not leak very much.

Then let the car cool down completely, take off the radiator cap and check the level there. If it's leaking coolant the level in the overflow container may look normal even when the radiator is half empty. At least that's the way it was on my old 323 when it had a pinhole leak in a cooling pipe. That car made noise under the dashboard of the "gurgling" variety from the air that got in where coolant should have been.

this is a good idea....i'll check the level at lunch. i haven't noticed any leaks though, although i haven't been diligently checking for any. when i looked under the hood this morning, i didn't see any obvious signs of a leak, but like you said, it could be small at this point.

aMaff · Mar 23, 2006

if I'm not mistaken, our cars don't have cabin filters. It's possible something's in 1 of the bottom vents. It happened to mine, it was hella annoying, and you'd hear a whistle any time the fan was on

drumsbeloud · Mar 23, 2006

aMaff said:
if I'm not mistaken, our cars don't have cabin filters. It's possible something's in 1 of the bottom vents. It happened to mine, it was hella annoying, and you'd hear a whistle any time the fan was on

Yeah, I thought of that. I tried turning the vents and AC on and off with no luck.

drumsbeloud · Mar 23, 2006

Well, I looked into this a bit more just now and came up withe the following obersvations:

- the hissing sound seems to be coming from below the dash in the center console, behind where the lower vents come out;
- no leaking coolant and the rad level is fine (I must have just been paranoid

) ;
- no apparent air leaks in the engine bay;
- the sound is present regardless of the HVAC setting;
- the sound is only present when the car is running (not in any other ignition position, even if the vents are on); and
- when I tap the gas from idle the sound seems to momentarily stop until the revs die back down a bit.

I have NO clue what this could be....anyone???

Kansei · Mar 23, 2006

aMaff said:
if I'm not mistaken, our cars don't have cabin filters. It's possible something's in 1 of the bottom vents. It happened to mine, it was hella annoying, and you'd hear a whistle any time the fan was on

Wait so is that why mine whistles at anything higher than the "1" fan speed??

It sounds like a plane is taking off... but of course on a much smaller scale.

drumsbeloud · Mar 23, 2006

I'm wondering if I have developed a leak in the HVAC hoses behind the dash feeding the floor vents?? I may have to start pulling s*** appart.

aMaff · Mar 24, 2006

zverg said:
Wait so is that why mine whistles at anything higher than the "1" fan speed??

It sounds like a plane is taking off... but of course on a much smaller scale.

it is entirely possible.

drumsbeloud · Mar 24, 2006

i just figured it out. it was a small leak under the dash in one of the boost gauge vacuum lines. i'm retarded.

hissing from under dash/firewall area

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