Smell of exhaust coming through A/C vents
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Newbie
Joined: Nov 2012
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From: Barbados
2011 E350 CDI Saloon 265bhp
Smell of exhaust coming through A/C vents
I have a 2011 E350 cdi and i can smell like exhaust fumes coming through my air condition vents and when outside is cold or at night the smell is stronger, even if i turn off the air condition i can still smell it through the vents. I have to change the air condition filter every 2 to 3 months and the filter has the same smell on it, someone must have had this problem i hate to drive this car because of this smell in the cabin, the car is doing 91000 miles. Awaiting your solutions Please Help !
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From: V E G A S
1922 Ford Model T / no OBD
Cabin inlet is in passenger side windshield gutter. The only way engine fumes can get there is when the gasket between gutter and engine bay is bad or misaligned.
Than you have to have exhaust leak on engine in the first place.
Than you have to have exhaust leak on engine in the first place.
Senior Member
Joined: Nov 2018
Posts: 443
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From: California
2013 E550 4MATIC - P1, P2, SPORT
I noticed that I tend to get exhaust smells when I don't have the car on "recycle" air mode. But I'm also hyper sensitive to the stench of car exhaust and I live in Southern California so there are cars everywhere. Have you tried putting the car on "Recycle" cabin air mode? If so and you're still getting the smell it's probably not exhaust but rather something hot/burning in the A/C system. (Apparently blower motors are a common cause of this.)
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From: V E G A S
1922 Ford Model T / no OBD
When you smell something in Recycle mode, you better have your charcoal filters replaced.
Those cars do have air quality sensors, who in case of bad outside air will switch to recycle and display warning on dashboard.
The only time I read somebody experienced that was from European member who drove in congested city.
Those cars do have air quality sensors, who in case of bad outside air will switch to recycle and display warning on dashboard.
The only time I read somebody experienced that was from European member who drove in congested city.
Thread Starter
Newbie
Joined: Nov 2012
Posts: 7
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From: Barbados
2011 E350 CDI Saloon 265bhp
When it is on recycle air mode i don't get the smell, but after a while the car switches back to fresh air mode, the smell is worst when outside is cold like at night or when it is raining, i change the cabin filter today and it had the smell on it. I know something on this car is causing this but me or dealers just cant figure it out
Newbie
Joined: Sep 2021
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E350 cdi
Did you find the issue?
When it is on recycle air mode i don't get the smell, but after a while the car switches back to fresh air mode, the smell is worst when outside is cold like at night or when it is raining, i change the cabin filter today and it had the smell on it. I know something on this car is causing this but me or dealers just cant figure it out
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MBWorld Fanatic!
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From: Pepper Pike Ohio
24 GLS580 '23 E450 4matic 12 E350 4Matic
could be as simple as your airbox above the battery is installed incorrectly, or the gasket is out of place, try looking at that first, they can be fussy to get correct.
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Thread Starter
Newbie
Joined: Nov 2012
Posts: 7
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From: Barbados
2011 E350 CDI Saloon 265bhp
Unfortunately, I still have the problem with this car, now I'm not so sure it's coming through the vents because although the car has been parked for the past 3 weeks waiting on an EGR valve, I can still smell this scent as soon as I open the doors or the trunk, one mechanic told me it might be the flap to the side of the trunk that is hidden by the back bumper might not be sealing properly, bit I'm frustrated.
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From: Pepper Pike Ohio
24 GLS580 '23 E450 4matic 12 E350 4Matic
Well, I love staying at Sandy Lane, you live in paradise. Maybe the smell is coming from the bad EGR valve, Again I suggest removing the airbox above the battery and insure the gasket isn't messed up and box is installed correctly. I changed out my battery in the auto parts store parking lot, then a month later, while detailing the engine bay, I noticed I did not re-install it correctly.
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From: US
2008 E350, 2012 ML350, 2014 E350, 2015 ML350
I would be 
if I smell exhaust fumes in the cabin; therefore, it is an urgent matter to fix in my book.
As explained by others already, there is no reason for exhaust fumes to smell anywhere in the engine bay or the cabin. On the back of the car, sure that is where the exhaust pipe ends.
Open the hood, with the car idling trying to pinpoint where any exhaust may be leaking: manifold to block gasket?, manifold to downpipe/cat union?, or oil leaking/dripping and making on top of a hot surface, say timing covers, PCV valve, manifold, alternator, AC compressor, anything.
The source of the unusual fumes around the engine bay must be fixed first and foremost. Sure, the rubber gasket around the engine bay could have deteriorated, nicked/cut/moved out during a previous visit to the engine bay or or suggested as well, the gasket between the AC filter holder and the AC air inlet in the gutter (as Kajtek1 suggested). There must plenty of unusual exhaust to create positive pressure under the hood to leak into the AC inlet (assuming AC is off and still comes through it).
As far as I know, the only entry points from the engine bay to the cabin are:
if I smell exhaust fumes in the cabin; therefore, it is an urgent matter to fix in my book.As explained by others already, there is no reason for exhaust fumes to smell anywhere in the engine bay or the cabin. On the back of the car, sure that is where the exhaust pipe ends.
Open the hood, with the car idling trying to pinpoint where any exhaust may be leaking: manifold to block gasket?, manifold to downpipe/cat union?, or oil leaking/dripping and making on top of a hot surface, say timing covers, PCV valve, manifold, alternator, AC compressor, anything.
The source of the unusual fumes around the engine bay must be fixed first and foremost. Sure, the rubber gasket around the engine bay could have deteriorated, nicked/cut/moved out during a previous visit to the engine bay or or suggested as well, the gasket between the AC filter holder and the AC air inlet in the gutter (as Kajtek1 suggested). There must plenty of unusual exhaust to create positive pressure under the hood to leak into the AC inlet (assuming AC is off and still comes through it).
As far as I know, the only entry points from the engine bay to the cabin are:
- the AC inlet
- the wires entry point behind the FrontSAM.
- the steering shaft entry/exit point
- the brake pedal pushrod to the brake booster (if still exists)
- Parking brake cable?
- Is there another one I am missing?
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From: US
2008 E350, 2012 ML350, 2014 E350, 2015 ML350
there should not exhaust gases under the hood unless there is a leak between the manifold and the engine, the manifold and the downpipe/cats, or holes in the pipes. Is the exhaust pipe some how clogged?
Junior Member
Joined: Oct 2011
Posts: 21
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From: bay area, CA
2011 e350 bluetec, 2016 gl350
My w212 smell exhaust or burnt oil smell after oil change from some dripped/spill oil. Then it had a leak at oil filter housing, which was fixed. The oil/exhaust smell keep lingering.
had the plastic cover underneath cleaned, spayed front and underneath engine clean. A bunch of dirt oil/soothe residue came off. The smell went away immediately.
if you decide to spay, must avoid or cover up electrical and sensors.
w212 cabin air inlet is separated from engine compartment, but not anywhere near airtight. Some vapor from engine and underside will get into air inlet.
had the plastic cover underneath cleaned, spayed front and underneath engine clean. A bunch of dirt oil/soothe residue came off. The smell went away immediately.
if you decide to spay, must avoid or cover up electrical and sensors.
w212 cabin air inlet is separated from engine compartment, but not anywhere near airtight. Some vapor from engine and underside will get into air inlet.
