help, question about weird hissing noise after shutoff

mikey19 · 08-05-2009, 09:45 PM

hey guys,

i just noticed today that after i turned my car off (from 2 hours of highway driving), there is a hissing noise coming from the front. I can make out that it sounds like water dripping and evaporating after hitting very hot metal.

Maybe it is the A/C system drain pipe? (I had my A/C on all the time). Is that normal? I thought the drain should drain the water directly to the ground. Why is the water hitting some hot metal and hissing??

Just wondering if I should get it checked out. I did notice a small puddle of water underneath my car.

Also is it weird to have my oil temp read >212F (100C) cruising at about 80-85 mph on the highway? the ambient temp was 32 to 34C.

Thanks

SoreHead · 08-05-2009, 09:51 PM

Quote:

Originally Posted by mikey19

hey guys,

i just noticed today that after i turned my car off (from 2 hours of highway driving), there is a hissing noise coming from the front. I can make out that it sounds like water dripping and evaporating after hitting very hot metal.

Maybe it is the A/C system drain pipe? (I had my A/C on all the time). Is that normal? I thought the drain should drain the water directly to the ground. Why is the water hitting some hot metal and hissing??

Just wondering if I should get it checked out. I did notice a small puddle of water underneath my car.

Also is it weird to have my oil temp read >212F (100C) cruising at about 80-85 mph on the highway? the ambient temp was 32 to 34C.

Thanks

Had the same thing last week and called into my dealer.
Turned out that it had rained here. (looking from the front) The left hand vent on the hood is decorative. The rain pools in there and there's a small rubber drain hole in the bottom. It doesn't drain very well so lets out the water inconsistently. I heard the noise and opened the hood. Nothing happened so I closed it and heard it again. The banging the hood closed made it release more water.

Stupid but no problem.

Hopefully that's the problem you're having. It'll be the passenger side in LHD countries and the drivers side in RHD countries. Hope this is the problem

niqui · 08-05-2009, 10:23 PM

its water dripping on the hot exhaust piping

zblake · 08-30-2011, 08:58 PM

Mine has done this the last two afternoons in a row. Oil temp is normal, and I have not been driving hard at all (in fact, doing a experiment to see if I can get the MPG over 20 just for kicks). Its only happening in the afternoon after ~40 miles of driving in ~85 degree F outside air, not in the morning on my way in where the air is ~60 degrees F. So, I'm pretty sure its condensate from the AC, but would like to hear if others have had this happen. Don't have time for a dealer check in if its no big deal. Coolant level is fine.

Asiarush · 08-30-2011, 09:48 PM

My car makes so many weird noises, i stopped paying attention to any of them !

coogs08 · 08-30-2011, 09:57 PM

the hissing sound is normal don't worry, it is indeed water from the a/c system hitting the high temp exhaust manifold.

Team Plutonium · 08-30-2011, 09:58 PM

Quote:

Originally Posted by niqui

its water dripping on the hot exhaust piping

This.

luis_m3 · 08-30-2011, 10:28 PM

Quote:

Originally Posted by Asiarush

My car makes so many weird noises, i stopped paying attention to any of them !

+1

1sikbmr · 08-30-2011, 10:31 PM

holy dead thread revival

08-05-2009, 09:45 PM	#1
mikey19 n00b Drives: 2008 E90 M3 / White / 6MT Join Date: Sep 2008 Location: Atlanta, GA Posts: 45 iTrader: (0)	help, question about weird hissing noise after shutoff hey guys, i just noticed today that after i turned my car off (from 2 hours of highway driving), there is a hissing noise coming from the front. I can make out that it sounds like water dripping and evaporating after hitting very hot metal. Maybe it is the A/C system drain pipe? (I had my A/C on all the time). Is that normal? I thought the drain should drain the water directly to the ground. Why is the water hitting some hot metal and hissing?? Just wondering if I should get it checked out. I did notice a small puddle of water underneath my car. Also is it weird to have my oil temp read >212F (100C) cruising at about 80-85 mph on the highway? the ambient temp was 32 to 34C. Thanks
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08-30-2011, 09:48 PM	#5
Asiarush Private First Class Drives: 2010 M3 Join Date: May 2010 Location: Los Angeles Posts: 176 iTrader: (2)	My car makes so many weird noises, i stopped paying attention to any of them ! __________________ 2010 M3 Jerez Black Metalic, Premium Package, Technology Package, M Double Clutch with driveLogic

08-30-2011, 10:31 PM	#9
1sikbmr Brigadier General Drives: E90 M3 6MT Join Date: Mar 2010 Location: New York Posts: 3,106 iTrader: (12)	holy dead thread revival __________________ E90 ///M3 6MT Atlantis Blue - Fox red Gloss black grilles/Red gills\|V1 hardwire\|Painted reflectors\|ZHP lighted shift knob\|VMR V710 silver\|GTS lip\|Lux custom 8k kit\|AA Green Filter\| AA Pulley\| RPI GTM Exhaust\|Sosi x-pipe\|BMW Performance Steering Wheel V1\|

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08-05-2009, 10:23 PM	#3
niqui Brigadier General Drives: Jet Black E92 M3 Join Date: Feb 2009 Location: Canada Posts: 3,096 iTrader: (7)	its water dripping on the hot exhaust piping

08-30-2011, 08:58 PM	#4
zblake Enlisted Member Drives: 09 AW M3 W/2-Doors & 6-gears Join Date: Aug 2011 Location: Norcal, USA Posts: 45 iTrader: (2)	Mine has done this the last two afternoons in a row. Oil temp is normal, and I have not been driving hard at all (in fact, doing a experiment to see if I can get the MPG over 20 just for kicks). Its only happening in the afternoon after ~40 miles of driving in ~85 degree F outside air, not in the morning on my way in where the air is ~60 degrees F. So, I'm pretty sure its condensate from the AC, but would like to hear if others have had this happen. Don't have time for a dealer check in if its no big deal. Coolant level is fine.

08-30-2011, 09:57 PM	#6
coogs08 Second Lieutenant Drives: 2009 M3 Join Date: Aug 2011 Location: Pearland, TX Posts: 203 iTrader: (1)	the hissing sound is normal don't worry, it is indeed water from the a/c system hitting the high temp exhaust manifold.